Showing papers by "University of East Anglia published in 1994"

Testing the iron hypothesis in ecosystems of the equatorial Pacific Ocean

Abstract: The idea that iron might limit phytoplankton growth in large regions of the ocean has been tested by enriching an area of 64 km2 in the open equatorial Pacific Ocean with iron This resulted in a doubling of plant biomass, a threefold increase in chlorophyll and a fourfold increase in plant production Similar increases were found in a chlorophyll-rich plume down-stream of the Galapagos Islands, which was naturally enriched in iron These findings indicate that iron limitation can control rates of phytoplankton productivity and biomass in the ocean

Arabidopsis Mutants Selected for Resistance to the Phytotoxin Coronatine Are Male Sterile, Insensitive to Methyl Jasmonate, and Resistant to a Bacterial Pathogen.

Abstract: The phytotoxin coronatine and the plant growth regulator methyl jasmonate (MeJA) caused similar growth-inhibitory effects on Arabidopsis seedlings. To test whether these two compounds have similar action, 14 independent coi1 (coronatine-insensitive) mutants of Arabidopsis were selected. The mutants segregated as single recessive Mendelian markers, and all were alleles at the coi1 locus. All coi1 mutants were also insensitive to MeJA and were male sterile. Both coronatine and MeJA inhibited root growth, stimulated anthocyanin accumulation, and increased the level of two proteins of ~31 and ~29 kD detected in SDS-polyacrylamide gels of wild-type Arabidopsis but caused none of these effects in the coi1 mutant. Coronatine and MeJA also induced the systemic appearance of proteinase inhibitor activity in tomato. The male-sterile flowers of the coi1 mutant produced abnormal pollen and had reduced level of an ~31-kD protein, which was abundant in the wild-type flowers. A coronatine-producing strain of Pseudomonas syringae grew in leaves of wild-type Arabidopsis to a population more than 100 times greater than it reached in the coi1 mutant. We conclude that coronatine mimics the action of MeJA and that coi1 controls a step in MeJA perception/response and in flower development.

Hemispheric Surface Air Temperature Variations: A Reanalysis and an Update to 1993.

Abstract: Land-based compilations of gridded monthly surface air temperature anomalies, averaged into hemispheric values for the last 140 years, have been available for climatological analyses for the last 10 years or so. The analysis techniques used in their construction, particularly the need for a common reference period, mean that it is difficult to include, retrospectively, any of the new temperature datasets now available for some countries. So, despite data availability improvements in some areas, the number of stations used has fallen since 1970, both in the hemispheric averages and in their constituent grid-box datasets. The present study is a reanalysis of both the existing and the newly available temperature datasets to produce a grid-box dataset of 5°×5° temperature anomalies. The reanalysis not only uses over 1000 more stations (2961 in total), principally covering the period from the 1920s to about 1990, but also arrests the decline of stations incorporated in real time for the latest years. ...

Spatial regression methods in dendroclimatology: a review and comparison of two techniques

Abstract: We review and compare two alternative spatial regression methods used in dendroclimatology to reconstruct climate from tree rings. These methods are orthogonal spatial regression (OSR) and canonical regression (CR). Both the OSR and CR methods have a common foundation in least-squares theory and converge to the same solution when all p candidate tree-ring predictors of climate are forced into the model. However, the perfomance of OSR and CR may differ when only subsets p' < p predictors are used. Theory cannot predict how either method is likely to perform when best-subset selection is applied, especially with regards to reconstruction accuracy. Consequently, empirical comparisons of OSR and CR are made using three tree-ring and climate networks from western Europe and eastern North America that have been used in previous dendroclimatic studies. These comparisons rely on a suite of regression model verification statistics to validate the accuracy of the climatic reconstructions produced by the best-subset models. The results indicate little real difference between OSR and CR, with each performing equally good or bad depending on the amount of recoverable climatic information in the tree rings. Canonical regression may perform slightly better in high signal-to-noise cases; conversely, OSR may perform slightly better when the signal-to-noise ratio is low. None of these apparent differences are large enough to select one method in preference to the other, however, and many more comparisons would be needed to determine if such indications are generally valid.

Analysis of the Streptomyces coelicolor sigE gene reveals the existence of a subfamily of eubacterial RNA polymerase sigma factors involved in the regulation of extracytoplasmic functions.

Abstract: sigma E, an RNA polymerase sigma factor of apparent M(r) 28,000, was previously identified by its ability to direct transcription from the P2 promoter of the agarose gene (dagA) of Streptomyces coelicolor. A degenerate oligonucleotide probe, designed from the N-terminal sequence of purified sigma E, was used to isolate the sigma E gene (sigE). The predicted sequence of sigma E shows greatest similarity to sequences of seven other proteins: Myxococcus xanthus CarQ, Pseudomonas aeruginosa AlgU, Pseudomonas syringae HrpL, Escherichia coli sigma E, Alcaligenes eutrophus CnrH, E. coli FecI, and Bacillus subtilis SigX, a protein of unknown function. These eight proteins define a subfamily of eubacterial RNA polymerase factors sufficiently different from other sigma s that, in many cases, they are not identified by standard similarity searching methods. Available information suggests that all of them regulate extracytoplasmic functions and that they function as effector molecules responding to extracytoplasmic stimuli. A. eutrophus CnrH appears to be a plasmid-encoded factor.

Competitive conditions in european banking

Abstract: In this paper we utilise the Rosse-Panzar statistic to assess competitive conditions in major EC banking markets between 1986 and 1989. Although EC banking legislation has established relatively free access to member country banking systems in recent years, our results indicate no change in market conduct of banks between 1986 and 1989. The results suggest that banks in Germany, the United Kingdom, France and Spain earned revenues as if under conditions of monopolistic competition in the period. In the case of Italy, they are consistent with banks having earned revenues as if under monopoly or conjectural variations short-run oligopoly conditions. We interpret the results as indicative of a lack of integration in EC banking markets and they thus underline the importance of the Second Banking Directive, the associated supervisory arrangements, and the elimination of capital controls as to achieving full integration.

Stratospheric aerosol growth and HNO3 gas phase depletion from coupled HNO3 and water uptake by liquid particles

Abstract: Aqueous sulphuric acid droplets, which constitute the background stratospheric aerosol, strongly absorb HNO3 and HCl under cold conditions. A thermodynamic model is used to predict partitioning of HNO3, HCl and H2O between gas and aerosol phases, and show that a 50-fold increase in aerosol volume, observed in the Arctic stratosphere as temperature approached the frost point (188.9 K), can be explained in terms of uptake of HNO3 and H2O by liquid aerosols. Calculated degrees of saturation of the droplets with respect to solid hydrates, taking into account the reduction in vapour phase HNO3, suggest that the droplets remain liquid to the frost point. Near this temperature, they can yield larger aerosol volumes than would have been the case for solid NAT (HNO3•3H2O) particles. The depletion of gas phase HNO3 into enhanced volumes of liquid aerosols resulting from volcanic eruptions may hamper NAT formation.

Fourier-Transform Raman and Fourier-Transform Infrared Spectroscopy (An Investigation of Five Higher Plant Cell Walls and Their Components).

Abstract: Infrared and Raman spectra of sequentially extracted primary cell walls and their pectic polymers were obtained from five angiosperm plants. Fourier-transform Raman spectrometry was shown to be a powerful tool for the investigation of primary cell-wall architecture at a molecular level, providing complementary information to that obtained by Fourier-transform infrared microspectroscopy. The use of an extraction procedure using imidazole instead of cyclohexane trans-1,2-N,N,N[prime],N[prime]-diaminotetraacetate allows the extension of the infrared spectral window for data interpretation from 1300 to 800 cm-1, to 2000 to 800 cm-1, and allows us to obtain Raman spectra from extracted cell-wall material. Wall constituents such as pectins, proteins, aromatic phenolics, cellulose, and hemicellulose have characteristic spectral features that can be used to identify and/or fingerprint these polymers without, in most cases, the need for any physical separation. The Gramineae (rice [Oryza sativa], polypogon [Polypogon fugax steud], and sweet corn [Zea mays]) are spectroscopically very different from the nongraminaceous monocotyledon (onion [Allium cepa]) and the dicotyledon (carrot [Daucus carota]); this reflects differences in chemical composition and cross-linking of the walls. The possibility of a taxonomic classification of plant cell walls based on infrared and Raman spectroscopies and the use of spectral fingerprinting for authentication and detection of adulteration of products rich in cell-wall materials are discussed.

Massage--the scientific basis of an ancient art: Part 2. Physiological and therapeutic effects.

Abstract: The physiological and therapeutic effects of massage are frequently questioned. This article reviews previous research into the effects of massage on blood flow and composition, oedema, connective tissue, muscle and the nervous system. Although further investigations are clearly required in certain areas, the discussion demonstrates that the use of massage in sports medicine can be justified according to orthodox scientific criteria.

The genetic consequences of long distance dispersal during colonization

Abstract: Rare long distance dispersal may have little impact on gene frequencies in established populations but it can dramatically increase gene flow during episodes of range expansion. We model the invasion of new territory by genetically distinct populations of the same species to investigate the dynamics of such episodes. If long distance dispersal is sufficiently frequent, the populations do not spread as a wave of advance but instead found intermingled isolates. We argue that this process can explain many otherwise puzzling patterns in the geographical distribution of alleles.

Dynamic reorientation of cortical microtubules, from transverse to longitudinal, in living plant cells

Abstract: The direction in which plant tissue cells expand is reflected in the alignment of microtubules in the cortical array When microtubules and coaligned wall microfibrils are arranged transversely around the cell, turgor pressure is chaneled into cell elongation However, various agents (such as wounding, ethylene, abscisic acid) can cause the microtubules to reorientate by 90 degrees so that they become aligned parallel to the cell's long axis, allowing lateral expansion instead of elongation The mechanism by which microtubules undergo rapid shifts of alignment is crucial to understanding growth control in plants, but because current models are derived from studies on fixed cells, nothing is known about the dynamics of converting one microtubule alignment to another Cells tend to have one predominant microtubule alignment--transverse, oblique, or longitudinal--but it is not established whether each represents a stable independent set that only changes by rounds of complete de- and repolymerization, or whether reorientation is a more continuous process involving movement of stable or dynamic microtubules By microinjecting pea (Pisum sativum) epidermal cells with rhodamine-conjugated brain tubulin and optically sectioning them by confocal laser scanning microscopy, we could follow labeled microtubules for up to 2 hr as they reorientate Reorientation does not occur by complete depolymerization of microtubules in one orientation followed by polymerization of a new array in another orientation Instead, increased numbers of discordant microtubules in nontransverse alignment appear in particular locations Neighboring microtubules then adopt the new alignment, so that there is a stage during which different alignments coexist before the array on the outer tangential cell face finally adopts a uniform steeply oblique/longitudinal configuration Rapid fluorescence recovery after photobleaching confirms that bundles of cortical microtubules are not stable but exhibit properties consistent with dynamic instability Dynamic microtubules offer a mechanism for rapid growth responses to a range of physiological stimuli

The FNR family of transcriptional regulators

Abstract: Homologues of the transcriptional regulator FNR fromEscherichia coli have been identified in a variety of taxonomically diverse bacterial species. Despite being structurally very similar, members of the FNR family have disparate regulatory roles. Those fromShewanella putrefaciens, Pseudomonas aeruginosa, Pseudomonas stutzeri andRhodopseudomonas palustris are functionally similar to FNR in that they regulate anaerobic respiration or carbon metabolism. Four rhizobial proteins (fromRhizobium meliloti, R. leguminosarum, B. japonicum andAzorhizobium caulinodans) are involved in the regulation of nitrogen fixation; a fifth (fromRhizobium strain IC3342) has unknown function. Two proteins from mammalian pathogens (Actinobacillus pleuropneumoniae andBordetella pertussis) may be involved in the regulation of toxin expression. The FNR protein ofVibrio fischeri regulates bioluminescence, and the function of the one known FNR homologue from a Gram-positive organism (Lactobacillus casei) remains to be elucidated. Some members of this family, like FNR itself, appear to function as sensors of oxygen availability, whereas others do not. The ability to sense and respond to oxygen limitation may be correlated with the presence of cysteine residues which, in the case of FNR, are thought to be involved in oxygen or redox sensing. The mechanism of DNA sequence recognition is probably conserved, or very similar, throughout this family. In a number of other Gram-negative species, there is good indirect evidence for the existence of FNR analogues; these includeAlcaligenes eutrophus, A. denitrificans, A. faecalis, Paracoccus denitrificans and a number ofPseudomonas species.

Validation of Large-Scale Precipitation Fields in General Circulation Models

Abstract: How well do the current generation of General Circulation Models (GCMs) simulate present-day climate? Answering this question is an important stage in the improvement of our ability to model global climate change The answer to the question will also determine the confidence that tiational and international bodies might place both in the projections of climate change generated by these models and in the regional climate change impact studies which use model output This paper quantitatively evaluates the performance of a number of model precipitation climatologies, using four ‘independent’ observed climatologies Three of the observed climatologies consist of mean monthly fields (JAEGER, LEGATES and IIASA), while the fourth is a new land-only time series of monthly precipitation from 1900 to 1992 (CRU0092) Comparisons are undertaken of global means and of the spatial pattern of the field of mean monthly precipitation A distinction is made between global and “terrestrial” precipitation fields CRU0092 includes interannual variability and therefore allows other validation exercises to be undertaken The importance of the observed reference period for model validation is assessed, and observed and modelled global precipitation sensitivities are compared These validation exercises reveal markedly different model performances and show that uncertainty about the ‘true’ observed precipitation hinder the task of model validation Validation analyses such as these, together with more detailed validation of the interannual variability and daily precipitation characteristics of model output, must remain an essential dimension both of ‘greenhouse climate’ predictions and of climate change impact analyses which rely upon GCM experiments

Real Space Manifestation of the First Sharp Diffraction Peak in the Structure Factor of Liquid and Glassy Materials

Abstract: The problem of those discernible features of the intermediate range order (IRO) which can be attributed to the first sharp diffraction peak (FSDP) observed in the structure factor of many liquid and glassy materials is approached by treating this peak as a distinct feature. It is found, by considering the measured partial structure factors, S αβ ( k ), for molten ZnCl 2 , GeSe 2 , MgCl 2 , NiBr 2 and Nil 2 and the measured total structure factors, F ( k ), for glassy SiO 2 , PS 4 and liquid CCl 4 , that the propensity of the FSDP to have a prominent effect on the underlying features of the IRO depends noticeably on the system type. Specifically, the FSDP confers a marked oscillatory character of periodicity 2π/ k 1 (where k 1 is the FSDP position) on the IRO when the local structural units, which give rise to the density fluctuations on the IRO scale, exist as stable entities for a timescale τ ≫ 5 × 10 -12 s. The FSDP therefore accounts for the discernible features of the underlying IRO for the viscous glass forming liquids ZnCl 2 and GeSe 2 , for the glasses SiO 2 and PS 4 , and for the molecular liquid CCl 4 . The influence of the FSDP on the IRO is less pronounced for molten MgCl 2 and is negligible for molten NiBr 2 and Nil 2 , both of which have a high cation mobility which leads to a relative instability of the Ni 2+ centred structural units. The effect on the FSDP of temperature and pressure are briefly considered as are the development of the FSDP in molten ZnX 2 (when X is changed from Cl to I to Br) and the minimum size of r -space model which is required if the FSDP is to be accurately predicted.

Primary and Secondary Values of Wetland Ecosystems

Abstract: Wetlands are continuously degraded in many parts of the world. One reason is the lack of the appropriate valuation of the multifunctionality of wetland. In an attempt to improve the understanding of the importance of this feature of wetlands an alternative classification of values is suggested; primary and secondary values. Primary value refers to the development and maintenance of ecosystems — their self-organizing capacity. Secondary values are defined as the outputs, life-support functions and services, generated by wetlands. Methods for measuring these values are discussed. Three case studies are presented which use different valuation methods and which to different degrees capture the primary and secondary values. It is concluded that only part of the total wetland value can be captured in monetary terms.

Structure of fast ion conducting and semiconducting glassy chalcogenide alloys.

Abstract: The method of isotopic substitution in neutron diffraction is used to measure the metal-metal partial structure factor ${S}_{\mathrm{MM}}(k)$ for the glassy fast ion conductor $g\ensuremath{-}\mathrm{A}{g}_{2}\mathrm{A}{s}_{3}\mathrm{S}{e}_{4}$ and for the glassy semiconductor $g\ensuremath{-}\mathrm{C}{u}_{2}\mathrm{A}{s}_{3}\mathrm{S}{e}_{4}$. The remaining partial structure factors are hence separated into two functions which comprise either the $M\ensuremath{-}\ensuremath{\mu}(\ensuremath{\mu}=\mathrm{As}\mathrm{or}\mathrm{Se})$ or $\ensuremath{\mu}\ensuremath{-}\ensuremath{\mu}$ species. It is found that the short range order of the network former $g\ensuremath{-}\mathrm{A}\mathrm{s}\mathrm{S}\mathrm{e}$ is not destroying on alloying with ${M}_{2}\mathrm{Se}$ and that the most significant structural differences occur with respect to the $M$ atom ordering.

Focal points in pure coordination games: An experimental investigation

Abstract: This paper reports an experimental investigation of the hypothesis that in coordination games, players draw on shared concepts of salience to identify ‘focal points’ on which they can coordinate. The experiment involves games in which equilibria can be distinguished from one another only in terms of the way strategies are labelled. The games are designed to test a number of specific hypotheses about the determinants of salience. These hypotheses are generally confirmed by the results of the experiment.

Summer moisture variability across europe, 1892-1991 : an analysis based on the palmer drought severity index

Abstract: Monthly Palmer Drought Severity Indices (PDSI) have been calculated for the period 1892–1991 over a 5° latitude by 5° longitude grid covering Europe and south-west Asia from 35 °N to 70 °N and 10 °W to 60 °E. These indices are used to describe the spatial and temporal details of relative moisture variability during summer (June-August). The full series of mean summer PDSI maps are presented. Over Europe as a whole, there has been a consistent (but statistically insignificant) increase in moisture supply throughout the period of record. The 1930s and 40s were exceptionally dry. The summer of 1947 was the driest, both in terms of average PDSI but also in terms of the spatial extent of moderate drought. However, the summer of 1921 was by far the most extreme when considering the spatial extent of severe drought conditions. Widespread drought conditions also prevailed over many regions of Europe during the 1890s. The wettest summers occurred in 1987 and 1916. The total area of Europe experiencing either severe dry or severe wet conditions has increased noteably during recent years. Nine regions of coherent summer moisture variability are objectively defined by orthogonal rotation of the principal components of the summer PDSI. The nine rotated components, which explain 60 per cent of total variability of this data set, represent moisture variability in north-western Europe (NWEUR), the north-west Mediterranean (NWMED), the lower Volga (LVOLG), central European Russia (CERUS), the north-east Mediterranean (NEMED), the southern Caspian Sea (SCASP), the Pechora Basin (PECHB), the Danube Basin (DANUB), and northern Fennoscandia (NFENN). The last 3 years have been very dry in NWEUR and NWMED. The most recent summer in our analysis, 1991, was the wettest on record in both CERUS and NEMED. Preliminary spectral analyses provide little evidence for a solar-moisture relationship in these European data over this period.

Massage--the scientific basis of an ancient art: Part 1. The techniques.

Abstract: Manual massage is a long established and effective therapy used for the relief of pain, swelling, muscle spasm and restricted movement. Latterly, various mechanical methods have appeared to complement the traditional manual techniques. Both manual and mechanical techniques are described systematically, together with a review of indications for use in sports medicine.

Temporal and spatial variability of biogenic particles fluxes during the JGOFS northeast Atlantic process studies at 47°N, 20°W

Abstract: Particle fluxes to 3100 m depth at 45°50′N, 19°30′W were measured using time-series sediment traps during a 17 month period encompassing 1989 and 1990 JGOFS spring bloom process studies in the northeast Atlantic. There was a marked intra-annual variability in fluxes of mass, particulate inorganic carbon (PIC), particulate organic carbon (POC) and opal, appearing as two major flux events in each year. In 1989, the first flux event represented the settlement of spring bloom-type material, whereas the second, in autumn, was heavily enriched in mucopolysaccharides. In 1990, in contrast, the two flux events comprised spring bloom-type material and arrived at depth at different times relative to the 1989 events. The intra- and interannual variability evident for all three biogenic components was most notable for POC: (i) the autumn 1989 event supplied twice as much POC to 3100 m as the earlier spring bloom settlement—a quite unexpected observation—and (ii) the annual average POC flux in 1989 was 3–4 times more than in 1990. A synthesis of process study datasets with sediment trap data enables an evaluation of the coupling of deep fluxes with surface-water events. Spatial variability of the 1989 deep flux events is assessed by comparing the sediment trap data reported here with those from a second site ∼ 100 km away (Honjo and Manganini,Deep-Sea Research II,40, 587–607, 1993). The timing and magnitude of the 1989 spring bloom settlement was indistinguishable in the two datasets, indicating no spatial variability in flux between these sites. In contrast, the autumn 1989 flux event was barely recorded at the second site. Given the biogeochemical importance of this latter event to deep waters, most notable in terms of its contribution to POC flux, this observation of deep-water mesoscale flux variability indicates a significant problem in determining regional carbon budgets. Construction of basin-scale budgets is a central goal of JGOFS and for this to be achieved further studies of mesoscale variability of particle flux are essential.

Contracts and Specific Investment: An Empirical Test of Transaction Cost Theory

Abstract: Empirical work has failed to keep pace with recent advances in transaction cost theory and the theory of contract. The first econometric analysis of its kind is reported by using a new data set of small subcuntractors making specific inputs for customers in the engineering industry. The use of formal contracts is found to be strongly associated with specific investment and other variables measuring technological complexity and vulnerability to potential opportunism by customers. Furthermore, despite typically long-term relationships, over half of subcontractors avoid making efficient, specific investments. Overall, we find strong support for the transaction cost theory of contracts.