Showing papers by "University of East Anglia published in 1989"
TL;DR: Studies of hybrid zones allow us to quantify the genetic differences responsible for speciation, to measure the diffusion of genes between diverging taxa, and to understand the spread of alternative adaptations.
Abstract: Many species are divided into a mosaic of genetically distinct populations, separated by narrow zones of hybridization. Studies of hybrid zones allow us to quantify the genetic differences responsible for speciation, to measure the diffusion of genes between diverging taxa, and to understand the spread of alternative adaptations.
1,041 citations
TL;DR: This work aims to demonstrate the efforts towards in-situ applicability of EMMARM, which aims to provide real-time information about concrete mechanical properties of EMTs.
Abstract: 1 Department of Clinical Chemistry, University Hospital, Rigshospitalet, Blegdamsvej 9, DK-2100 Copenhagen, Denmark; 2 School of Biological Sciences, University of East Anglia, Norwich NR4 7T J, UK; 3 Department of Clinical Physiology and Nuclear Medicine, University Hospital, Rigshospitalet, Blegdamsvej 9, DK-2100 Copenhagen, Denmark; 4 Department of Chemistry BC, Royal Danish School of Pharmacy, Universitetsparken 2, DK-2100 Copenhagen, Denmark; s MRC Molecular Neurobiology Unit, University of Cambridge Medical School, Hills Road, Cambridge CB2 2QH, UK; and 6 Thrombosis Group, Copenhagen Science Park Symbion, Haraldsgade 68, DK-2100 Copenhagen, Denmark
540 citations
TL;DR: In this paper, it was shown that Forster's result arises as the short-range limit of a more general dipoledipole interaction based on virtual photon coupling, and the result can be identified with the classical result for radiative transfer.
264 citations
TL;DR: In this paper, it has been hypothesized that climate may be noticeably affected by changes in cloud condensation nuclei (CCN) concentrations, caused by either changes in the flux of dimethylsulphide (DMS) from the oceans1,2 and/or by man-made increases in sulphur dioxide (SO2) into the atmosphere3.
Abstract: IT has been hypothesized that climate may be noticeably affected by changes in cloud condensation nuclei (CCN) concentrations, caused either by changes in the flux of dimethylsulphide (DMS) from the oceans1,2 and/or by man-made increases in the flux of sulphur dioxide (SO2) into the atmosphere3. When oxidized, the sulphur compounds produce non-sea-salt sulphate (n.s.s.-SO2−4,) aerosols, which may act as CCNs. The CCN changes affect climate by altering the number density and size distribution of droplets in clouds, and hence their albedo. Here I am concerned primarily with the possible effects of SO2. Because the increase in SO2 emissions has been largely in the Northern Hemisphere, this raises the possibility of a cooling of the Northern Hemisphere relative to the Southern3. By comparing observed differences in hemispheric-mean temperatures with results from a simple climate model, one can place limits on the possible magnitude of any SO2-derived forcing. The upper limit is sufficiently large that the effects of SO2 may have significantly offset the temperature changes that have resulted from the greenhouse effect.
223 citations
TL;DR: Sodium perborate in acetic acid is an effective reagent for the oxidation of aromatic aldehydes to carboxylic acids, iodoarenes to (diacetoxyiodo)arenes, azines to N -oxides, and various types of sulphur heterocycles to S, S -dioxides.
183 citations
TL;DR: In this paper, the authors proposed a tracking strategy, in which livestock densities are encouraged to follow, more closely than at present, variations in rainfall, and the establishment of grazing territories controlled by specific "communities" is a prerequisite for the promotion of the tracking strategy.
Abstract: Communal rangeland management policies in Botswana and Zimbabwe are based on incorrect technical assumptions about the stability of semiarid rangeland, the nature of rangeland degradation, and the benefits of destocking. Consequently, inappropriate policies, stressing the need to destock and stabilise the rangelands, are pursued. Acknowledgement of the great instability but intrinsic resilience of rangeland would encourage the Governments to regard the opportunistic stocking strategies of the agro-pastoralists of the Communal Areas more favourably. However, degradation of rangelands is occurring, although at varying rates. This justifies the promotion of a "tracking strategy', in which livestock densities are encouraged to follow, more closely than at present, variations in rainfall. The establishment of grazing territories controlled by specific "communities' may be a prerequisite for the promotion of the tracking strategy, and for communal rangeland management and improvement. However, the establishment of such territories must take into account social equity, institutional problems and transaction costs, as well as spatial and temporal variation in rangeland resources.
182 citations
TL;DR: The GUS gene, created by ligating the Aspergillus nidulans glyceraldehyde 3-phosphate dehydrogenase promoter to the coding sequence of the E. coli uidA gene, forms the basis for a versatile and sensitive reporter gene system for industrial and phytopathogenic filamentous fungi.
Abstract: A chimaeric β-glucuronidase (GUS) gene has been created by ligating the Aspergillus nidulans glyceraldehyde 3-phosphate dehydrogenase promoter to the coding sequence of the E. coli uidA gene. Cotransformation of this vector into A. nidulans, A. niger and the tomato pathogen Fulvia fulva (syn. Cladosporium fulvum (Cooke)) resulted in the expression of β-glucuronidase. GUS activity was detected by growth on agar media containing X-gluc and by enzyme assays of mycelial extracts. Expression of the gene in F. fulva transformants was also easily detectable during growth in plants and did not affect pathogenicity. These results form the basis for a versatile and sensitive reporter gene system for industrial and phytopathogenic filamentous fungi.
179 citations
TL;DR: Comparison of the number of haustorial connections made to each species with the abundance of roots in the soil shows that R. minor is a highly selective parasite, but that the selectivity is not consistent between populations or between plants from different parts of the same population.
Abstract: Rhinanthus minor (Yellow-rattle) is a widespread hemiparasitic plant of grassland habitats throughout Britain. Association analysis of the dune vegetation at Holme-next-the-Sea in eastern England revealed only two potential host plants through positive association. In contrast direct examination of the root systems revealed haustorial connections with 20 host species. The number of species parasitized by one plant ranged from one to seven. Data from another four sites in Britain and one in central Europe indicate that the natural host range of R. minor encompasses at least 50 species from 18 families with 22% in the Leguminosae and 30% in the Gramineae. Comparison of the number of haustorial connections made to each species with the abundance of roots in the soil shows that R. minor is a highly selective parasite, but that the selectivity is not consistent between populations or between plants from different parts of the same population. The reasons for host selectivity are discussed.
161 citations
148 citations
TL;DR: A new hypothesis is put forward to account for the switch from aquatic plant to phytoplankton dominance in eutrophicated shallow lakes and suggests that each state is buffered against increased loading by mechanisms involving plant and algal physiology and zooplankon grazer populations.
Abstract: SUMMARY. 1. In 1982 and 1983 sets of experimental ponds were left with their submerged plant communities intact (plant ponds) or were cleared manually of them (cleared ponds). The ponds were all fertilized with ammonium nitrate and with variable amounts of phosphate. In 1982 fish were removed from the ponds. Zooplankton communities were dominated by large Cladocera with Daphnia prominent in the cleared ponds and Simocephalus in the plant ponds. There was no detectable effect of differential phosphorus additions on zooplankton communities or populations.
2. In 1983 zooplanktivorous fish (mainly roach) were stocked in the ponds. In the plant ponds the fish did not survive, probably through severe deoxygenation and the zooplankton community again included large-bodied Simocephalus. Fish survival was variable in the cleared ponds. Where fish stocks were absent or low (0.5–1 g m−2) a Daphnia- dominated community persisted; at intermediate fish stocks (18.1 g m−2) Eudiaptomus gracilis was predominant and where fish stock was high (22.8–29.1 g m−2) Bosmina longirostris, and cyclopoid copepods dominated the communities. Mean biomass of the zooplankton community declined with increase in fish stock to between 5.1 and 18.1 g m−2 then increased.
3. On the basis of results from the experimental ponds and elsewhere, a new hypothesis is put forward to account for the switch from aquatic plant to phytoplankton dominance in eutrophicated shallow lakes. It envisages dominance by either group to be possible as alternative states over a wide range of high nutrient loadings. It suggests that each state is buffered against increased loading by mechanisms involving plant and algal physiology and zooplankton grazer populations. The nature of the buffers and the reasons by which one state may be switched to the other are, discussed.
142 citations
TL;DR: The evidence supposed to provide a distinction between genetic coupling and coevolution of male and female components is reviewed and in most cases the data are inadequate, but in two examples coupling is clearly absent.
Abstract: Genetic coupling and coevolution of male and female components have been seen as alternative solutions to the problem of maintaining coordination between the sexes during evolutionary divergence of mate recognition systems. The evidence supposed to provide a distinction between these alternatives is reviewed. In most cases the data are inadequate, but in two examples coupling is clearly absent and in no case is it firmly established as the explanation for the maintenance of coordination. The distinction may only be useful in systems controlled by a few major loci as opposed to polygenic systems.
TL;DR: In this paper, partial pressure and heat of dilution data were used to determine the activity coefficient of weak electrolyte NH{sub 3} ({gamma}{sub NH{ sub 3}}), in pure aqueous solutions where dissociation is not significant.
Abstract: The thermodynamic Henry's law constant (K{sub H}/mol kg{sup {minus}1} atm{sup {minus}1}) of the weak electrolyte NH{sub 3} is described by the equation ln (K{sub H}) = {minus}8.09694 + 3917.507/T {minus}0.00314T, from 372 to 313 K. Measured NH{sub 3} solubilities in both pure aqueous and multicomponent solutions agree well with calculations using the Pitzer thermodynamic model to predict osmotic and activity coefficients. Partial pressure and heat of dilution data were used to determine the activity coefficient of NH{sub 3} ({gamma}{sub NH{sub 3}}). In pure aqueous solutions where dissociation is not significant this is given by {gamma}{sub NH{sub 3}} = exp(2m{sub NH{sub 3}}{lambda}{sub NH{sub 3}}{sub NH{sub 3}}), where {lambda}{sub NH{sub 3}}{sub NH{sub 3}} = 0.033161 - 21.12816/T + 4665.1461/T{sup 2} from 273 to 313 K. Ion-NH{sub 3} interaction parameters were obtained by using partial pressure, salt solubility, and partitioning data for the following ions at 298.15 K; Li{sup +}, Na{sup +}, K{sup +}, NH{sub 4}{sup +}, Mg{sup 2+}, Ca{sup 2+}, Sr{sup 2+}, Ba{sup 2+}, F{sup {minus}}, Cl{sup {minus}}, Br{sup {minus}}, I{sup {minus}}, OH{sup {minus}}, CNS{sup {minus}}, NO{sub 3}{sup {minus}}, NO{sub 2}{sup {minus}}, ClO{sub 3}{sup {minus}}, ClO{sub 4}{sup {minus}}, S{sup 2{minus}}, SO{sub 3}{sup 2{minus}}, CH{sub 3}COO{sup {minus}}, HCOO{sup {minus}} and (COO){sub 2}{sup 2{minus}}.more » Parameter values are found to be simply related to ion charge and size.« less
TL;DR: This cluster provides a plausible model for the ligation states of the [4Fe-4S]1+ core in the S = 3/2 cluster of the iron protein of nitrogenase and in Bacillus subtilis glutamine:phosphoribosyl pyrophosphate amidotransferase.
Abstract: Desulfovibrio africanus ferredoxin III is a protein (Mr 6585) containing one [3Fe-4S]1+,0 and one [4Fe-4S]2+,1+ core cluster when aerobically isolated. The amino acid sequence contains only seven cysteine residues, the minimum required to ligand these two clusters. Cyclic voltammery by means of direct electrochemistry at a pyrolytic-graphite-'edge' electrode promoted by neomycin shows that, when reduced, the [3Fe-4S]0 centre reacts rapidly with Fe(II) ion to form a [4Fe-4S]2+ cluster. The latter, which can be reduced at a redox potential similar to that of the other [4Fe-4S] cluster, must include non-thiolate ligation. We propose that the carboxylate side chain of aspartic acid-14 is the most likely candidate, since this amino acid occupies the position of a cysteine residue in the sequence typical of an 8Fe ferredoxin. The magnetic properties at liquid-He temperature of this novel cluster, studied by low-temperature magnetic-c.d. and e.p.r. spectroscopy, are diamagnetic in the oxidized state and S = 3/2 in the one-electron-reduced state. This cluster provides a plausible model for the ligation states of the [4Fe-4S]1+ core in the S = 3/2 cluster of the iron protein of nitrogenase and in Bacillus subtilis glutamine:phosphoribosyl pyrophosphate amidotransferase.
TL;DR: In this paper, a data set derived from the United States Historical Climate Network has been compared to two global land-based temperature data sets that have been commonly cited in connection with the detection of the greenhouse effect and in other studies of climate change.
Abstract: A data set derived from the United States Historical Climate Network has been compared to two global land-based temperature data sets that have been commonly cited in connection with the detection of the greenhouse effect and in other studies of climate change Results indicate that in the United States the two global land-based temperature data sets have an urban bias between +61°C and +04°C over the twentieth century (1901–84) This bias is as large or larger than the overall temperature trend in the United States during this time period, +016°C/84 yr Temperature trends indicate an increasing temperature from the turn of the century to the 1930s but a decrease thereafter By comparison, the global temperature trends during the same period are between +04°C/84 yr and +06°C/84 yr At this time, we can only speculate on the magnitude of the urban bias in the global land-based data sets for other parts of the globe, but the magnitude of the bias in the United States compared to the overall te
TL;DR: Ponds dominated by plants continued to have low phytoplankton populations even when fish were stocked, and in ponds cleared of plants there were significant relationships between cholorophyll a concentration with Daphnia biomass and log stock of potentially zooplanktivorous fish (positive).
Abstract: SUMMARY. 1 During eutrophication of shallow lakes, communities of submerged plants are often replaced by dense phytoplankton populations, but the mechanism by which this occurs is obscure though often assumed to involve shading.
2. This paper introduces a series investigating this change and describes a system of experimental ponds which were variously fertilized with nitrogen and phosphorus, had fish added or removed, and had their submerged aquatic plants cleared or left intact.
3. Fertilization with phosphate and ammonium nitrate in quantities effectively greater than those in a series of lakes in the adjacent Norfolk Broads, which have lost their submerged plants, did not displace the plant populations.
4. Total phosphorus and soluble reactive phosphorus concentrations in the water did not increase much with increasing loading in the presence of submerged plants but did so if the plants were manually cleared. Ammonium and nitrate concentrations were kept low, despite large additions in both plant dominated and manually cleared ponds.
5. In the absence of fish there were modest increases in chlorophyll a concentrations with phosphorus loading in the presence or absence of submerged plants. The concentrations achieved, however, were much lower than anticipated probably because of grazing by large-bodied Cladocera.
6. Ponds dominated by plants continued to have low phytoplankton populations even when fish were stocked. Low fish survival in these ponds permitted grazing zooplankters to flourish. In ponds cleared of plants, however, there were significant relationships between cholorophyll a concentration with Daphnia biomass (inverse) and log stock of potentially zooplanktivorous fish (positive). There was a significant relationship between chlorophyll a and total phosphorus concentrations in the plant and cleared ponds in 1982 but only in the plant ponds in 1983. In all cases the phytoplankton communities were dominated by small, often flagellated, organisms.
TL;DR: It is postulated that the great abundance of the primary host of R. padi, bird cherry, and the spring planting of cereals in colder climates such as in Finland are major factors contributing to the differences in pest status of this aphid between Britain and in Scandinavia.
Abstract: The biology and pest status of Rhopalosiphum padi (L.) in Europe are critically reviewed. New data are presented and the temporal occurrence of the aphid and its host-plants considered. In Britain, R. padi is a pest mainly because of its ability to transmit virus diseases, in particular barley yellow dwarf virus. In other European countries, especially in Scandinavia, R. padi is a pest in its own right. Predator and parasite complexes in Britain and Finland are compared and contrasted. The occurrence of R. padi as a pest of cereals in Europe is compared with that of Sitobion avenae (F.) and Metopolophium dirhodum (Walker). It is postulated that the great abundance of the primary host of R. padi, bird cherry (Prunus padus), and the spring planting of cereals in colder climates such as in Finland are major factors contributing to the differences in pest status of this aphid between Britain and in Scandinavia.
TL;DR: In this article, an unease that a labour process approach to managerial work, if it is to be based upon simplistic assumptions that management itself is a labor process will actually obs...
Abstract: This paper is motivated by an unease that a labour process approach to managerial work, if it is to be based upon simplistic assumptions that management itself is a labour process will actually obs...
Journal Article•
TL;DR: Parallel studies of the ionic balance and membrane permeability characteristics of normal human lenses indicate that in the ageing process there is an increasing contribution to membrane ion traffic from a channel, or channels, that permit Na+, K+ and Ca2+ to pass.
Abstract: Parallel studies of the ionic balance and membrane permeability characteristics of normal human lenses were carried out in three countries (USA, England and Italy) Similar age-related changes were found in each laboratory The lens membrane potential and resistance declined markedly with age while internal Na+ and free Ca2+ increased There was a concomitant stimulation of Na+ and K+ transmembrane fluxes These data indicate that in the ageing process there is an increasing contribution to membrane ion traffic from a channel, or channels, that permit Na+, K+ and Ca2+ to pass The increase in permeability coincides exactly with the increase in optical density that occurs in the ageing human lens
TL;DR: In this article, a detailed study of the propagation of homogeneous plane elastic waves which are essential to a basic understanding of the behaviour of surface waves is presented. But the authors do not consider the effect of the shape of the outer sheet of the slowness surface.
Abstract: In relation to transversely isotropic media, this paper presents a detailed study of those aspects of the propagation of homogeneous plane elastic waves which are essential to a basic understanding of the behaviour of surface waves. It is first shown how the ordering of the speeds of plane waves provides, directly and simply, a means of classifying the chosen materials, with the class label specifying the broad structure of the slowness surface and the location of its singular points. An examination of the shape of the outer sheet of the slowness surface follows, providing inter alia a complete account of the incidence of the various types of transonic states. The discussion turns next to exceptional waves, that is homogeneous plane waves which leave free of traction some family of parallel planes. The subset of the plane waves possessing this property is determined, after which the subset of the exceptional waves serving as limiting waves for an exceptional transonic state is picked out. Exceptional transonic states occur only when the axis of material symmetry lies either in the reference plane or at right angles to the reference vector and these orientations of the axis are referred to as $\alpha$ and $\beta$ configurations respectively. The exceptional states are arranged in a threefold classification, one class consisting of a continuous set of $\alpha$ configurations and the others discrete $\beta$ configurations. The paper ends with calculations of the limiting speed of the transonic state for the totality of $\alpha$ and $\beta$ configurations.
TL;DR: One way of looking at the relationship between educational theory and the professional knowledge of teachers is to see the former as a set of ideas about some aspect of education which has been constructed within a specialised academic discipline by experts who have mastered its particular standards of inquiry as mentioned in this paper.
Abstract: One way of looking at the relationship between educational theory and the professional knowledge of teachers is to see the former as a set of ideas about some aspect
of education which has been constructed within a specialised academic discipline
by experts who have mastered its particular standards of inquiry. The knowledge
and understanding conveyed by such a theory can then be applied by teachers in
learning to teach effectively. Professional knowledge, on this view of educational
theory, consists of a theoretical understanding of ideas about various aspects of
education drawn from disciplines such as philosophy, psychology, sociology and
history, plus ‘knowing how’ to apply them in particular practical situations.
TL;DR: The significance of urban warming effect on large-scale and hemispheric mean temperature series is assessed using estimates of the urbanization bias for stations in the United States produced by Karl et al. as mentioned in this paper.
Abstract: The significance of the urban warming effect on large-scale and hemispheric mean temperature series is assessed using estimates of the urbanization bias for stations in the United States produced by Karl et al. It is concluded that the Northern Hemisphere landmass average recently compiled by Jones et al. may contain a spurious warming trend which is, at the maximum, 0.1°C over the first eight decades of the twentieth century. This is considerably less than the long-term warming trend observed over the same period.
TL;DR: Individual virgin females of two races of Podisma pedestris were mated sequentially with a male of each race in one or other reciprocal orders, giving four types of double matings, confirming the previous indication of assortative fertilization producing homogamy, and revealing first sperm precedence, which is rare in insects.
Abstract: Sperm precedence and homogamy across a hybrid zone in the alpine grasshopper Podisma pedestris
TL;DR: RefReflection-absorption infrared spectra of the series of C 2 to C 6 normal alkanes in the form of both monolayers and multilayers on Pt(111) are presented as mentioned in this paper.
TL;DR: It is shown that reversible unmediated electrochemistry of the two iron-sulphur clusters can be obtained by using a pyrolytic-graphite-'edge' carbon electrode in the presence of an appropriate aminoglycoside, neomycin or tobramycin, as promoter.
Abstract: Desulfovibrio africanus ferredoxin III is a monomeric protein (Mr 6585) containing seven cysteine residues and 7-8 iron atoms and 6-8 atoms of acid-labile sulphur. It is shown that reversible unmediated electrochemistry of the two iron-sulphur clusters can be obtained by using a pyrolytic-graphite-‘edge’ carbon electrode in the presence of an appropriate aminoglycoside, neomycin or tobramycin, as promoter. Cyclic voltammetry reveals two well-defined reversible waves with E0′ = -140 +/- 10 mV and -410 +/- 5 mV (standard hydrogen electrode) at 2 degrees C. Bulk reduction confirms that each of these corresponds to a one-electron process. Low-temperature e.p.r. and magnetic-c.d. spectroscopy identify the higher-potential redox couple with a cluster of core [3Fe-4S]1+.0 and the lower with a [4Fe-4S]2+.1+ centre. The low-temperature magnetic-c.d. spectra and magnetization properties of the three-iron cluster show that it is essentially identical with that in Desulfovibrio gigas ferredoxin II. We assign cysteine-11, -17 and -51 as ligands of the [3Fe-4S] core and cysteine-21, -41, -44 and -47 to the [4Fe-4S] centre.
TL;DR: In this article, the authors examine why land management practices are not carried out, and what can be done about this, focusing on the need to obtain an accurate explanation of why degradation has occurred.
Abstract: The paper examines why land management practices are not carried out, and what can be done about this. If focuses on the need to obtain an accurate explanation of why degradation has occurred, and highlights the need to examine: whether degradation really is taking place; the identification of those for whom land degradation is, or will be, a problem; the identification of why land degradation is taking place; the need to find solutions and means to reach them (ie policy formulation).
TL;DR: In this article, the growth frequency of speleothems is examined using a cumulative distributed error frequency method applied to 341 uncontaminated uranium-series age determinations, and the curves derived are shown to be statistically stable.
TL;DR: In this article, the authors discuss technical development and peasant impoverishment: land use policy in Zimbabwe's Midlands Province and discuss the role of land use in economic development and economic impoverishment.
Abstract: (1989). Technical development and peasant impoverishment: land use policy in Zimbabwe's Midlands Province. Journal of Southern African Studies: Vol. 15, Politics of Conservation in Southern Africa, pp. 287-305.
TL;DR: Since brain water content is increased in normal appearing white matter of multiple sclerosis patients, and is significantly reduced by high-dose methylprednisolone, resolution of oedema may contribute to the rapid spontaneous or corticosteroid induced symptomatic recovery that characterises the disease in its early stages.
Abstract: Magnetic resonance imaging was performed on 50 patients with clinically definite or probable multiple sclerosis before and 15 days after starting treatment with intravenous methylprednisolone (0.5 g daily for 5 days). Scans were abnormal in 49 patients. New lesions had appeared on the second scan in nine individuals and in seven a single pre-existing lesion appeared to have become smaller but in no case were lesions seen to disappear. Two patients showed both reduction in the size of an abnormal area and development of a single new lesion indicating that corticosteroids do not appear rapidly to alter the process underlying plaque formation. Measurements of relaxation times were performed in 12 randomly selected patients. All showed elevated values in normal appearing white matter but not cortex before treatment compared with 18 healthy controls. After treatment a significant decrease of T1 and T2 was observed in cortex, and of T1 alone in normal appearing white matter. No significant change could be detected within lesions, a finding attributed to the wide range of relaxation values observed at these sites before treatment. Since brain water content is increased in normal appearing white matter of multiple sclerosis patients, and is significantly reduced by high-dose methylprednisolone, resolution of oedema may contribute to the rapid spontaneous or corticosteroid induced symptomatic recovery that characterises the disease in its early stages.
TL;DR: It is suggested that floating reedswamps have become more vulnerable to disintegration through changes in nitrate-nitrogen relative to potassium concentrations in Broads' water, likely to be compounded by a large decrease in the biomass of horizontal rhizomes infloating reed growing at high nitrate concentrations compared with reed rooted in the sediment.