Showing papers by "University of East Anglia published in 1992"

Fennoscandian summers from ad 500: temperature changes on short and long timescales

Abstract: Quantitative estimates of 1480 years of summer temperatures in northern Fennoscandia have previously been derived from continuous treering records from northern Sweden. Here we show the results of spectral analyses of these data. Only a few peaks in the spectra are consistently significant when the data are analyzed over a number of sub-periods. Relatively timestable peaks are apparent at periods of 2.1, 2.5, 3.1, 3.6, 4.8, ∼ 32–33 and for a range between ∼ 55–100 years. These results offer no strong evidence for solar-related forcing of summer temperatures in these regions. Our previously published reconstruction was limited in its ability to represent long-timescale temperature change because of the method used to standardize the original tree-ring data. Here we employ an alternative standardization technique which enables us to capture temperature change on longer timescales. Considerable variance is now reconstructed on timescales of several centuries. In comparison with modern normals (1951–70) generally extended periods when cool conditions prevailed, prior to the start of the instrumental record, include 500–700, 790–870, 1110–1150, 1190–1360, 1570–1750 (A.D.) with the most significant cold troughs centred on about 660, 800, 1140, 1580–1620 and 1640. Predominantly warm conditions occurred in 720–790, 870–1110 and 1360–1570 with peaks of warmth around 750, 930, 990, 1060, 1090, 1160, 1410, 1430, 1760 and 1820.

Implications for climate and sea level of revised IPCC emissions scenarios

Abstract: A new set of greenhouse gas emissions scenarios has been produced by the Intergovernmental Panel on Climate Change (IPCC). Incorporating these into models that also include the effects of C02 fertilization, feedback from stratospheric ozone depletion and the radiative effects of sulphate aerosols yields new projections for radiative forcing of climate and for changes in global-mean temperature and sea level. Changes in temperature and sea level are predicted to be less severe than those estimated previously, but are still far beyond the limits of natural variability.

Electrical signalling and systemic proteinase inhibitor induction in the wounded plant

Abstract: THE wound response of several plant species involves the activation of proteinase inhibitor (pin) genes and the accumulation of pin proteins at the local site of injury and systemically throughout the unwounded aerial regions of the plant1,2. It has been suggested that a mobile chemical signal is the causal agent linking the local wound stimulus to the distant systemic response, and candidates such as oligosaccharides3, abscisic acid4 and a polypeptide5,6 have been put forward. But the speed of transmission is high for the transport of a chemical signal in the phloem. The wound response of tomato plants can be inhibited by salicylic acid7 and agents like fusicoccin that affect ion transport8, and wounding by heat9 or physical injury produces electrical activity that has similarities to the epithelial conduction system10 used to transmit a stimulus in the defence responses of some lower animals11. Here we design experiments to distinguish between a phloem-transmissible chemical signal and a physically propagated signal based on electrical activity. We show that translocation in the phloem of tomato seedlings can be completely inhibited without effect on the systemic accumulation of pin transcripts and pin activity, and without hindrance to propagated electrical signals.

Rainfall changes in Africa: 1931–1960 to 1961–1990

Abstract: It remains common for 1941–1970, or even 1931–1960, climatological rainfall normals to be used in applied climate studies in Africa. Often this is due simply to the easier availability of station means or rainfall maps for these periods. Such rainfall statistics, however, are unrepresentative of recent decades, especially the new World Meteorological Organization standard period, 1961–1990. In this paper two independent 30-year rainfall climatologies for Africa are constructed from 572 quality controlled station time series of monthly rainfall. These climatologies are for the periods 1931–1960 and 1961–1990 and are constructed on a 5° grid. Differences between these two 30-year periods are determined with respect to mean seasonal rainfall, interannual variability and rainfall seasonality. Latitudinal profiles of mean seasonal rainfall emphasize the dominance of reduced Sahelian rainfall in the rainfall changes occurring over this period. This decline in boreal summer rainfall is shown to be statistically significant using field comparison statistics. Annual time series of regional rainfall anomalies for the Sahel, East Africa and south-western Africa are constructed; these three time series possess quite different interannual rainfall characteristics. Possible explanations for these observed rainfall changes are discussed with respect to land cover changes, global sea-surface temperature patterns, and greenhouse gas forcing.

Thermodynamics of multicomponent, miscible, ionic solutions. 2. Mixtures including unsymmetrical electrolytes

Abstract: Model equation for the excess Gibbs energy and solvent and solute activity efficients (given previously for symmetrical salt systems) are here developed for mixtures containing an indefinite number of ions of arbitrary charge, over the entire concentration range. The equations are expressed on a mole fraction basis and comprise a Debye-Huckel term extended to include the effects of unsymmetrical mixing, and a Margules expansion carried out to the fow suffix level

A 1951–80 global land precipitation climatology for the evaluation of general circulation models

Abstract: Previous evaluations of model precipitation fields have suffered from two weaknesses; they have used only mean observed climatologies which have prevented an explicit evaluation of interannual variability, and they have generally failed to quantify the significance of differences between model and observed fields. To rectify these weaknesses, a global precipitation climatology is required which is designed with model evaluation in mind. This paper describes such a climatology representative of the period 1951–80. The climatology is based on historical gauge-precipitation measurements from over 2500 land-based station time series representing over 28% of the Earth's surface. It is necessarily biased towards terrestrial areas. The climatology (CRU5180) is derived from month-by-month gridbox precipitation estimates at 5° resolution. Although other global precipitation climatologies exist, this is the first one to have used a consistent reference period for each station, and to include the details of interannual variability. Fields of mean seasonal and annual precipitation and mean temporal variability are presented, and the variability of global-mean precipitation over 1951–80 assessed. The resulting mean monthly global precipitation fields are compared briefly with two other observed climatologies used for model evaluation, those prepared by Jaeger and Legates and Willmott. The global and hemispheric means, mean seasonal cycles, and spatial patterns of the three cimatologies are compared. Although based on a smaller set of stations than Legates and Willmott, the CRU5180 precipitation estimates agree closely with their uncorrected climatology.

Bead: explorations in information visualization

Abstract: We describe work on the visualization of bibliographic data and, to aid in this task, the application of numerical techniques for multidimensional scaling.Many areas of scientific research involve complex multivariate data. One example of this is Information Retrieval. Document comparisons may be done using a large number of variables. Such conditions do not favour the more well-known methods of visualization and graphical analysis, as it is rarely feasible to map each variable onto one aspect of even a three-dimensional, coloured and textured space.Bead is a prototype system for the graphically-based exploration of information. In this system, articles in a bibliography are represented by particles in 3-space. By using physically-based modelling techniques to take advantage of fast methods for the approximation of potential fields, we represent the relationships between articles by their relative spatial positions. Inter-particle forces tend to make similar articles move closer to one another and dissimilar ones move apart. The result is a 3D scene which can be used to visualize patterns in the high-D information space.

Global surface air temperature variations during the twentieth century: Part 1, spatial, temporal and seasonal details

Abstract: This paper is an up-to-date review of instrumentally-recorded, seasonal, surface temperature change across the land and marine regions of the world during the twentieth century. This is the first part of a two part series. The second part will deal with the interpretation of proxy-climate data in terms of large-scale hemispheric or global-scale temperature averages for the Holocene.In Part 1, we review the uncertainties associated with combining land and marine instrumental records to produce regional-average series. The surface air temperature of the world has warmed 0.5°C since the middle of the nineteenth century. The warming in the Northern Hemisphere only occurred in winter, spring and autumn. Summers are now no warmer than in the 1860s and 1870s. The same half-degree warming is seen in all seasons in the Southern Hemisphere.Spatial patterns of temperature anomalies during two warm decades, the 1930s and 1980s, all vary from season to season. Temperatures during the 1980s were by far the warmest in t...

Laboratory study of cannibalism and interspecific predation in ladybirds

Abstract: . 1 In the absence of aphids, adult females of Adalia bipunctata (L.) showed a greater reluctance to eat eggs than males. 2 Eggs and young larvae were more vulnerable to cannibalism than older larvae and starved larvae were more vulnerable than well-fed larvae. 3 Both egg and larval cannibalism is inversely related to the abundance of aphids. 4 Eggs are a better food, in terms of larval growth and survival, than aphids. 5 In the absence of aphids interspecific predation occurred, but not equally, between the coccinellids A.bipunctata, A.decempunctata (L.), Coccinella septempunctata L. and C.undecempunctata L. 6 Larvae and adults of A. bipunctata and C.septempunctata were reluctant to eat conspecific eggs painted with a water extract of the other species' eggs and larvae of C. septempunctata were more likely to die after eating a few eggs of A.bipunctata than vice versa. 7 These results indicate that cannibalism occurs mainly when aphid prey is scarce and is adaptive in that it improves the chances of survival, and coccinellids, to varying degrees, are defended against interspecific predation.

HIV risk factors in three geographic strata of rural Rakai District, Uganda

Abstract: Objectives: To examine risk factors for HIV-1 infection in three geographic strata (main road trading centers that service local and international traffic, small trading villages on secondary dirt roads that serve as foci tor local communications, and agricultural villages off main and secondary roads) in Rakai District, Uganda. Design and methods: Serological, sociodemographic, knowledge/behaviors and health survey conducted in 21 randomly selected community clusters; complete data were collected for 1292 consenting adults. Results: Fifteen per cent of the men and 24% of the women were HIV-1-positive. On univariate analysis, several sociodemographic and behavioral factors were significantly associated with risk of HIV infection, including age, place of residence, travel, occupation, marital status, number of sex partners, sex for money or gifts, history of sexually transmitted disease (STD), and history of injections. On multivariate analysis, age, residence and number of sex partners remained significantly associated with HIV infection in both sexes; a history of STD and not having been circumcised were significant in men. There was a significant interaction between place of residence and reported number of sex partners: for any given level of sexual activity, the risk of HIV infection was markedly increased if the background community prevalence was high. Conclusion: Sexual transmission appears to be the primary behavioral risk factor for infection, but the risks associated with this factor vary substantially between the three geographic strata. These data can be used to design targeted interventions.

Attack strategy of ladybird beetles (Coccinellidae): factors shaping their numerical response

Abstract: Temporal changes in aphid abundance pose a considerable challenge to ovipositing aphidophagous ladybirds, as in order to maximize their fitness they need to synchronize their reproduction with the early development of aphid populations. Field census data and laboratory experiments were used to determine how ovipositing females of the two-spot ladybird, Adalia bipunctata (L.), assess whether an aphid population is suitable for exploitation. In the field, two-spot ladybirds usually laid eggs well before aphid populations peaked in abundance. In the laboratory they showed a marked reduction in their reproductive numerical response in the presence of larvae of their own species but not of other aphidophagous ladybirds. At the highest aphid density this was not a consequence of competition for food between larvae and ovipositing females. In the presence of conspecific larvae gravid females were very active and as a consequence more likely to leave an area, and when confined with other conspecific females or larvae laid fewer eggs and later than females kept on their own. The extent of the inhibition of egg laying is negatively correlated with the rate of encounter with larvae. Thus it is proposed that gravid females appear mainly to use the presence of conspecific larvae to assess the potential of an aphid colony for supporting the development of their offspring.

Child abuse and the bureaucratisation of social work

Abstract: Child abuse became a public issue in the early 1970s. The alleged failure of social workers and welfare agencies to prevent children being killed by their parents and caretakers led to changes in the practice and organisation in child abuse work. The way public inquiries and government departments framed the problem of child abuse produced solutions which were essentially legalistic and bureaucratic. No longer was the aim to rehabilitate poorly functioning families, but to protect children from dangerous parents. But in order to achieve this aim, it was first necessary to identify the factors that would allow child protection agencies to recognise which families were dangerous and which were not. Once these factors were identified, it was possible to develop administrative systems that would facilitate the collection and analysis of information obtained during the investigation of suspected families. These systems allowed welfare agencies to identify ‘high risk’ cases. During the translation of the problem of child abuse into a set of judicial and bureaucratic procedures, therapeutically orientated professional practices found themselves out-manoeuvered. The translation witnessed the production of social workers as ‘passive agents’, a new cognitive perspective on the problem of child abuse, and a contribution to the bureaucratisation of child care practice.

Sulfur: the plankton/climate connection

Abstract: Question (Aiken et al.): Given the uncertainties involved in the calculation of air-sea exchange of gases such as DMS, is it possible to assess by other methods the importance of natural versus anthropogenic sulfur emissions? Answer: In our paper we discuss various approaches that have been taken to estimate the rate of emission of DMS from the oceans including models (Erikson et al. 1990, Thompson et al. 1990) and the use of observed concentration fields of DMS combined with knowledge of air-sea transfer velocity (Andreae 1986, Bates et al. 1987b). In addition measurements of MSA in atmospheric aerosols can be used to infer the emission of DMS into the atmosphere (J. Prospero, University of Miami, pers. commun.). Many studies (not reviewed in this paper) have investigated the emissions of sulfur from manmade sources. In all these attempts, an assessment is often made of the relative importance of the two sources, although the methodology used to calculate biogenic and anthropogenic sources are fundamentally different. The only consistent approach we are aware of, which has the potential to directly ascribe sulfur in the atmosphere to its major sources, is through the use of sulfur isotope signature measurements. The method relies on the sulfur isotope signature of fossil fuels being significantly different from that of DMS and its oxidation products. This approach shows great promise and is currently being investigated in our laboratory.

Aperiodic tiles

Abstract: A set of tiles (closed topological disks) is calledaperiodic if there exist tilings of the plane by tiles congruent to those in the set, but no such tiling has any translational symmetry. Several aperiodic sets have been discussed in the literature. We consider a number of aperiodic sets which were briefly described in the recent bookTilings and Patterns, but for which no proofs of their aperiodic character were given. These proofs are presented here in detail, using a technique with goes back to R. M. Robinson and Roger Penrose.

Domains of the catalytically self-sufficient cytochrome P-450 BM-3. Genetic construction, overexpression, purification and spectroscopic characterization.

Abstract: 1. The gene CYP102 encoding cytochrome P-450 BM-3 and subgenes encoding the cytochrome P-450 and cytochrome P-450 reductase domains have been cloned in Escherichia coli. 2. The protein products of these genes have been overexpressed and purified to homogeneity. 3. The cytochrome P-450 domain is purified in the ferric low-spin state, but is readily converted into the high-spin state by addition of the substrate palmitate (Ks = 1 microM). The cytochrome P-450 reductase domain readily reduces cytochrome c. Mixing the two domains reconstitutes only about one-thousandth of the fatty acid hydroxylase activity associated with the intact cytochrome P-450 BM-3. 4. The X-band e.p.r. spectra of both the cytochrome P-450 domain and intact cytochrome P-450 BM-3 give g-values indicating low-spin ferric haem. The spectra are virtually identical with those of the equivalent form of cytochrome P-450 cam indicating that the haem ligation in cytochrome P-450 BM-3 is identical with that of cytochrome P-450 cam. 5. Resonance Raman spectra of the substrate-free and substrate-bound forms of the cytochrome P-450 domain are given. Spectral differences in comparison with cytochrome P-450 cam may reflect subtle electronic differences between the respective haem environments.

Solar cycle length, greenhouse forcing and global climate

Abstract: THE recent rise in global-mean surface air temperature is widely thought to be the result of increasing atmospheric concentrations of greenhouse gases1–3, but there are discrepancies between the predicted response of the atmosphere to this radiative forcing and the observed temperature changes1–5. Solar irradiance fluctuations have been proposed as a possible explanation for these discrepancies, and various solar properties (for example, radius6, smoothed sunspot number7 or cycle length8) have been suggested as proxies for solar irradiance variations in the absence of direct data. Here we model the effects of a combination of greenhouse and solar-cycle-length forcing and compare the results with observed temperatures. We find that this forcing combination can explain many features of the temperature record, although the results must be interpreted cautiously; even with optimized solar forcing, most of the recent warming trend is explained by greenhouse forcing.

Evidence for photochemical control of ozone concentrations in unpolluted marine air

Abstract: OZONE in the troposphere is an important greenhouse gas, and a key participant in the oxidation of other trace species, but the mechanisms for its formation and destruction are not fully understood. In polluted regions of the Northern Hemisphere, seasonal increases in ozone concentration have been observed1,2; such changes could arise from photochemical reactions3–6, but they could also involve transport from the ozone-rich stratosphere7. In remote, unpolluted (low-Nox) regions, photochemical theory predicts net destruction of ozone8. Here we present observations of a large summer minimum in ozone concentration in the unpolluted marine boundary layer of the Southern Hemisphere. Our results show a clear link between ozone loss and hydrogen peroxide production in the region, demonstrating that in situ photo-chemistry, rather than transport, is the major cause of the seasonal ozone cycle in the boundary layer. These findings emphasize the role of photochemical processes in the lower atmosphere, and may suggest only a limited role for transport in other, more polluted regions.

The role of the hemiparasitic annual Rhinanthus minor in determining grassland community structure.

Abstract: Rhinanthus minor (yellow-rattle) is a widespread hemiparasitic plant of grassland habitats throughout Great Britain. It is usually considered to be indicative of species-rich grassland, but in a survey of 14 habitats throughout Britain it was found that R. minor at the time of flowering normally occupied relatively low-diversity patches within areas of high diversity as determined by the number of species, Simpson's Index and the Shannon-Wiener Index. Following the death of adult plants of R. minor in the summer it was shown that the pattern of species diversity changed such that by the time R. minor germinated in the following spring the differences between the areas containing and not containing R. minor were much less distinct. A perturbation experiment in which R. minor was removed from four sites indicated that the effect of the removal of R. minor on the development of community structure over the next year was to increase species diversity on three of the sites and decrease it on the fourth. Those species which responded to the removal of R. minor by an increase in abundance were shown to be preferred hosts. All three lines of evidence point to the fact R. minor has a significant effect on the species diversity of the communities in which it grows by selectively parasitizing components of the flora and modifying the competitive relationships between plants. However, as the communities generally responded to the removal of R. minor by an increase in diversity and as the general survey indicated that R. minor is generally associated with areas of low diversity it would appear that the plants which are selectively parasitized are generally not the competitive dominants in the community.

Can conservation and development be coupled among pastoral people? An examination of the Maasai of the Ngorongoro Conservation Area Tanzania.

Abstract: One of the new paradigms in sub-Saharan Africa is that conservation of natural resources can be coupled with human development. This paper addresses this paradigm and its application to the Maasai who live in the Ngorongoro Conservation Area in Tanzania. The assertion is that environmental conservation has been achieved but the Maasai have suffered serious economic and nutritional declines. The evidence is the increasing number of pastoralists who are unable to support themselves and the extent of malnutrition in the population. These trends among the Maasai are not unique and can also be evidenced through pastoral regions of East Africa. Discussion focuses on background information on environmental conservation and human development in East Africa the current situation in northern Tanzania and conclusions and recommendations for an action plan. The results were based on an analysis of data from the census survey conducted in 1987 an aerial survey and fieldwork in 1989 an opportunistic sample of herd owners and a nutritional survey in 1987. Findings indicate that livestock production is declining 16% of children <5 years are malnourished and 41% are undernourished. The nutritional survey was conducted just after the rainy season and probably reflects the seasonal minimum rather than maximum. The average adult Body Mass Index suggested acceptable nutritional levels but further examination revealed 12% of males and 15% of females were probably malnourished. The findings support the findings of Arhem Rodgers and Homewood. This analysis suggests a different cause: the lack of livestock to sell. Authorities blame the declines on Maasai mismanagement while the Maasai blame the restrictions on grazing prevention of burning and ban on agriculture. An examination of conditions in the larger region suggests that economic declines have been occurring over the past 20 years and are exacerbated by the lack of employment opportunities. Bans on agriculture were based on myths and not on the importance to the Maasai diets. Recommendations are to explain the findings within a regional context to evaluate policy to determine on what factual basis it rests to reduce tensions between pastoralists and conservationists and to provide alternative sources of income. Nine specific development interventions are indicated which stress community participation in development and conservation approaches.

A field study using the fungicide benomyl to investigate the effect of mycorrhizal fungi on plant fitness.

Abstract: The effect of vesicular-arbuscular mycorrhiza (VAM) on the fecundity ofVulpia ciliata ssp.ambigua was investigated at two field sites in eastern England by applying the fungicide benomyl to reduce VAM infection. The application of benomyl at the two sites produced very different results. At one site the application of the fungicide reduced the fecundity of plants whereas at the other fecundity was increased. At the first site the reduction in fecundity was linked to a significant reduction in VAM infection on the sprayed plants. The mechanism of the benefit associated with the VAM infection is however unclear: there was no treatment effect on morphology or on phosphorus inflow. At the second site, where fecundity was increased, there was only a negligible amount of VAM infection amongst the unsprayed plants and it is suggested that the increase in fecundity with the application of benomyl may have resulted from a reduction in infection by other, presumably pathogenic, fungi. The value of VAM fungi to the host plant may therefore not be restricted to physiological benefits. They may also provide protection to the plant by competing for space with other species of pathogenic fungi.

CfT-I: an LTR-retrotransposon in Cladosporium fulvum, a fungal pathogen of tomato.

Abstract: A retrotransposon from the fungal tomato pathogen Cladosporium fulvum (syn. Fulvia fulva) has been isolated and characterised. It is 6968 bp in length and bounded by identical long terminal repeats of 427 bp; 5 bp target-site duplications were found. Putative first- and second-strand primer binding sites were identified. Three long open reading frames (ORFs) are predicted from the sequence. The first has homology to retroviral gag genes. The second includes sequences homologous to protease, reverse transcriptase, RNAse H and integrase, in that order. Sequence comparisons of the predicted ORFs indicate that this element is closely related to the gypsy class of LTR retrotransposons. Races of the pathogen exhibit polymorphisms in their complement of at least 25 copies of the sequence. Virus-like particles which co-sediment with reverse transcriptase activity were observed in homogenates of the fungus. This is the first report of an LTR retrotransposon in a filamentous fungus.

Testing New Theories of Choice under Uncertainty using the Common Consequence Effect

Abstract: A generalised common consequence problem is used to contrast the predictions of expected utility theory and several new theories of choice under uncertainty. An experiment designed to test these predictions is reported. Systematic violations of expected utility theory are detected but although a consistent pattern emerges from the data, it offers little support for any of the new theories. The analysis is extended to test predictions which are unique to regret theory and significant regret effects are detected.