Showing papers by "University of East Anglia published in 1990"

A 1,400-year tree-ring record of summer temperatures in Fennoscandia

Abstract: Tree-ring data have been used to reconstruct the mean summer (April-August) temperature of northern Fennoscandia for each year from AD 500 to the present. Summer temperatures have fluctuated markedly on annual, decadal and century timescales. There is little evidence for the existence of a Medieval Warm Epoch, and the Little Ice Age seems to be confined to the relatively short period between 1570 and 1650. This challenges the popular idea that these events were the major climate excursions of the first millennium, occurring synchronously throughout Europe in all seasons. An analysis of past warming trends suggests that any summer warming induced by greenhouse gases may not be detectable in this region until after 2030.

Assessment of urbanization effects in time series of surface air temperature over land

Abstract: RECORDS of hemispheric average temperatures from land regions for the past 100 years provide crucial input to the debate over global warming1–4. Despite careful use of the basic station data in some of these compilations of hemispheric temperature1,2,4–6, there have been suggestions7,8 that a proportion of the 0.5 °C warming seen on a century timescale may be related to urbanization influences—local warming caused by the effects of urban development. We examine here an extensive set of rural-station temperature data for three regions of the world: European parts of the Soviet Union, eastern Australia and eastern China. When combined with similar analyses for the contiguous United States9,10, the results are representative of 20% of the land area of the Northern Hemisphere and 10% of the Southern Hemisphere. The results show that the urbanization influence in two of the most widely used hemispheric data sets1,2,4 is, at most, an order of magnitude less than the warming seen on a century timescale.

Natural variability of the climate system and detection of the greenhouse effect

Abstract: GLOBAL mean temperatures show considerable variability on all timescales. The causes of this variability are usually classified as external or internal1, and the variations themselves may be usefully subdivided into low-frequency variability (timescale ≳= 10 years) and high-frequency variability (≲=10 years). Virtually nothing is known about the nature or magnitude of internally generated, low-frequency variability. There is some evidence from models, however, that this variability may be quite large1,2, possibly causing fluctuations in global mean temperature of up to 0.4 °C over periods of thirty years or more (see ref. 2, Fig. 1). Here we show how the ocean may produce low-frequency climate variability by passive modulation of natural forcing, to produce substantial trends in global mean temperature on the century timescale. Simulations with a simple climate model are used to determine the main controls on internally generated low-frequency variability, and show that natural trends of up to 0.3 °C may occur over intervals of up to 100 years. Although the magnitude of such trends is unexpectedly large, it is insufficient to explain the observed global warming during the twentieth century.

Cloning, disruption, and transcriptional analysis of three RNA polymerase sigma factor genes of Streptomyces coelicolor A3(2).

Abstract: The rpoD gene of Myxococcus xanthus was used as a probe to isolate three Streptomyces coelicolor genes, hrdB, hrdC, and hrdD, which appear to encode RNA polymerase sigma factors extremely similar to the sigma 70 polypeptide of Escherichia coli. Gene disruption experiments suggested that hrdB is essential in S. coelicolor A3(2) but showed that hrdC and hrdD mutants are viable and are apparently unaffected in differentiation, gross morphology, and antibiotic production. S1 nuclease mapping showed that hrdB and hrdD, but not hrdC, were transcribed in liquid culture. The most upstream of two hrdD promoters is internal to an open reading frame (ORF X) on the opposite strand. The predicted product of this gene is homologous to the phosphinothricin acetyltransferases of Streptomyces hygroscopicus and Streptomyces viridochromogenes. The possible significance of the overlapping and divergent transcription of hrdD and ORF X is discussed. A general method for in vivo gene replacement was developed that allowed a positive selection for the desired mutants even in the absence of a mutant phenotype; it was used to isolate a stable hrdC mutant.

On open boundary conditions for three dimensional primitive equation ocean circulation models

Abstract: An open boundary condition is constructed for three dimensional primitive equation ocean circulation models. The boundary condition utilises dominant balances in the governing equations to assist calculations of variables at the boundary. The boundary condition can be used in two forms. Firstly as a passive one in which there is no forcing at the boundary and phenomena generated within the domain of interest can propagate outwards without distorting the interior. Secondly as an active condition where a model is forced by the boundary condition. Three simple idealised tests are performed to verify the open boundary condition, (1) a passive condition to test the outflow of free Kelvin waves, (2) an active condition during the spin up phase of an ocean, (3) finally an example of the use of the condition in a tropical ocean.

Gas transfer velocities in lakes measured with SF6

Abstract: The experimentally-determined relationships between air-water gas transfer velocity and windspeed are presented for two small, rapidly wind mixed lakes in upland SW England. High-precision estimates of the gas transfer velocity, k , with daily resolution, were derived by monitoring the rate of evasion from the lakes of added sulphur hexafluoride, SF 6 , an inert, sparingly soluble, man-made gaseous tracer. Corresponding data on in situ wind speeds and directions, and surface water temperatures were automatically logged as a time series of 4 min averages, using a battery-powered device. The results significantly extend the existing field database and show a strong dependence of k , normalized to CO 2 at 20 °C, on windspeed in the range ∼ 2–13 m s−1, corrected to a height of 10 m. No correlation was found between k and wind direction. The data are fitted with two least-squares straight lines which intersect at a windspeed of 9.5 ± 3 m/s (at z = 10 m), beyond which significant steepening of the k vs. windspeed relationship implies a transition from the “rough surface” to “breaking wave” regime, in broad agreement with previous conclusions. Nevertheless, the data scatter about the fitted lines exceeds that which would be predicted from the associated analytical uncertainties. This implies the observed relationships between k and windspeed are not unique and therefore that additional factors must be important in determining k . DOI: 10.1034/j.1600-0889.1990.t01-3-00006.x

Determination of the total unsaturation in oils and margarines by fourier transform raman spectroscopy

Abstract: An improved Raman spectroscopic procedure for the determination of the total unsaturation in oils and fats using Fourier Transform Raman (FT-Raman) spectroscopy is described. An important advantage of FT-Raman for these samples is that the spectra are fluorescence-free unlike dispersive Raman which often uses visible excitation. Samples can be analyzed without any pre-treatment thus eliminating the need for dissolution in toxic solvents. The short acquisition time of FT-Raman and the ease of application allowed for a rapid sample turnover.

Interactive interpolation and approximation by Be´zier polynomials

Abstract: One of the main problems in computer-aided design is how to input shape information to the computer. The paper describes a method developed for the interactive interpolation and approximation of curves which has been found in practice to provide a natural interface between the mathematically unsophisticated user and the computer.

The Mechanism by Which Aphids Adhere to Smooth Surfaces

Abstract: 1.The adhesive force acting between the adhesive organs and substratum for a number of aphid species has been studied. In the case of Aphis fabae , the force per foot is about 10 μN. This is much the same on both glass (amphiphilic) and silanized glass (hydrophobic) surfaces. The adhesive force is about 20 times greater than the gravitational force tending to detach each foot of an inverted aphid. 2.The mechanism of adhesion was considered. Direct van der Waals forces and viscous force were shown to be trivial and electrostatic force and muscular force were shown to be improbable. An adhesive force resulting from surface tension at an air-fluid interface was shown to be adequate and likely. 3.Evidence was collected that the working fluid of the adhesive organ has the properties of a dilute aqueous solution of a surfactant. There is a considerable reserve of fluid, presumably in the cuticle of the adhesive organ.

Holocene climatic change, 14C wiggles and variations in solar irradiance

Abstract: Evidence from the advances and retreats of alpine glaciers during the Holocene suggests that there were at least 14 century-timescale cool periods similar to the recent Little Ice Age. Here, we examine the hypothesis that these cool periods were caused by reductions in solar irradiance. A statistically significant correlation is found between the global glacial advance and retreat chronology of Rothlisberger and variations in atmospheric $^{14}$C concentration. A simple energy-balance climate model is used to show that the mean reduction of solar irradiance during times of maximum $^{14}$C anomaly like the Maunder Minimum would have to have been between 0.22 and 0.55% to have caused these cool periods. If a similar solar irradiance perturbation began early in the 21st century, the associated climate effects would be noticeable, but still considerably less than those expected to result from future greenhouse gas concentration increases.

Equilibrium partial pressures and mean activity and osmotic coefficients of 0-100 % nitric acid as a function of temperature

Abstract: Rational activity and osmotic coefficients and Henry's law constants K{sub Hx} (for the reaction HNO{sub 3(g)} = H{sup +}{sub (aq)} + NO{sub 3}{sup {minus}}{sub (aq)}), given as functions of temperature, enable p(H{sub 2}O) and p(HNO{sub 3}) to be calculated from {minus}60 to 120{degree}C, 0-100% HNO{sub 3}. Apparent molal enthalpies, heat capacities, and activity coefficients (derived from electromotive force (emf), freezing point, and partial pressure data) are represented with the use of the species-interaction models of Pitzer. Equations for the partial molal functions are given. The Henry's law constant is evaluated from p(HNO{sub 3}) data at 298.15 K, tabulated heats of formation, and heat capacities. Calculated p(H{sub 2}O) and p(HNO{sub 3}) over the entire concentration range agree with available data over 5 orders of magnitude of p(H{sub 2}O) and 7 orders of magnitude of p(HNO{sub 3}).

Rapid determination of water droplet size distributions by PFG-NMR

Abstract: In 1972 Packer and Rees described a method for the determination of droplet size distributions in emulsions using the pulsed field gradient (PFG) NMR spin—echo technique. This paper describes an improved method, based on this earlier work, which is directed at the routine determination of water droplet size distributions of water-in-oil emulsions. The improvement is based on the recognition that a set of echo attenuation values (R) as a function of the field gradient pulse width, obtained under conditions where R is independent of the time allowed for diffusion, contains all the necessary information on the water droplet size distribution. The parameters of a log-normal distribution of water droplet sizes are easily obtained from a small number of measurements which are then compared with a matrix of sets of theoretical echo attenuations, representing different combinations of these parameters, using a simple computer program. The method is described and examples of results are shown. The effect of temperature on the measurements is discussed.

Detection and suppression of impulsive noise in speech communication systems

Abstract: In the paper a method is presented for the removal of impulsive disturbances from noisy speech and musical signals. The algorithm is based on a detection-interpolation scheme. The design of the impulsive noise detector subsystem is motivated by the observation that linear prediction systems are quite adequate for the modelling of speech signals whereas they can not model impulsive disturbances. It is shown that transforming the speech signal to the glottal excitation may result in significant reduction of the scale of the speech signal to almost that of the excitation signal whereas the scale of impulsive noise does not decrease. This can lead to a significant improvement in the detectability of the noise pulses. Further improvement may be obtained by the application of a matched filter to the noisy excitation signal. The signal samples that are obliterated by impulsive noise are discarded and interpolated. The interpolation method produces a least squared error estimate of the missing samples using speech samples in the vicinity of the missing block and an estimate of the LPC model of the signal. It is shown that the performance of the interpolation system improves significantly when the LPC model incorporates long term correlation structure in addition to the usual short term correlation parameters.

AIDS and HIV infection in Uganda--are more women infected than men?

Abstract: In countries in sub-Saharan Africa, HIV is transmitted primarily heterosexually. HIV infection and AIDS in women not only affects women's health but also has implications for the other members of society. Maternal infection is the source of most childhood HIV infection in Africa and maternal health is a strong predictor of child survival. In Uganda, a review of passive AIDS surveillance has shown almost equal numbers of clinical cases reported in men and women. However, in three population-based HIV serosurveys, women were consistently found to have a higher infection rate (approximately 1.4 times) than men. In addition, both AIDS case surveillance and seroprevalence studies demonstrate an earlier age of presentation and mean age of infection in women. The higher rate of HIV infection in women suggests either differential rates of transmission between women and men, higher rates of female sexual exposure to infected men, or longer survival among HIV-infected women compared with men. Although further studies are required to illuminate both the biology and the epidemiology of heterosexual HIV transmission in Africa, these findings of earlier and higher infection rates in women have important implications for women's health and child survival in Uganda and indicate the need for specially targeted interventions to reduce transmission in this group.

Bis-methionine axial ligation of haem in bacterioferritin from Pseudomonas aeruginosa

Abstract: THE iron-containing bacterioferritins1–6 contain the protoporphyrin IX haem group5. It has been established that Escherichia coli cytochrome b1, cytochrome b557 and bacterioferritin are identical7. The optical spectra at room temperature of the haem group show it to be predominantly low-spin in both the ferrous and ferric states8. The nature of the axial ligands binding the haem group to the polypeptide has, however, remained unknown. Low-spin, bis-coordinate haem centres in proteins typically have a role in rapid electron transfer as redox changes at the metal ion lead to little structural rearrangement9. There are only four amino acids with side-chains that have ligand field strengths sufficient to generate the low-spin state of haem, namely, histidine, lysine, methionine and cysteine. Hence there are, potentially, ten different pairs of these four ligands which could be discovered in electron transferhaemoproteins. To date only three have been established with certainty. They are bis-histidine, as in mammalian cytochrome b5 (ref. 10), methionine-histidine, typified by cytochrome c (ref. 11) and lysine-histidine, recently recognized by spectroscopic methods in cytochrome f (ref. 12). Here we report the electron paramagnetic resonance and near infrared magnetic circular dichroism spectra of the oxidized state of Ps. aeruginosa bacterioferritin which enable the axial ligands to be identified as the thioether side chains of two methionine residues, a ligation scheme not previously reported for haem in any protein.

Why Not in My Backyard? A Radical Interpretation of Public Opposition to the Deep Disposal of Radioactive Waste in the United Kingdom:

Abstract: Public opposition to the disposal of radioactive waste in the United Kingdom has often been characterised as being largely of the “not in my backyard” (NIMBY) variety. In this paper, the history of policy for the management of radioactive waste in the United Kingdom is reviewed, highlighting the numerous shifts in policy and the combination of political and technical factors at work. It is argued that much of the public distrust of plans for radioactive waste and the public perception of the risks of the disposal of radioactive waste is heavily influenced by that history.Reviewed in particular in this paper is the recent public discussion programme on the deep disposal of radioactive wastes. With use of the writings of C Wright Mills, it is argued that public responses to that programme of discussion reflect certain ‘vocabularies of motive’ which are constrained by the broad framework of policy for the management of radioactive waste in the United Kingdom. Rather than being simply NIMBY responses, many of...

Antarctic Temperatures over the Present Century—A Study of the Early Expedition Record

Abstract: Air temperature records for 26 expeditions to Antarctica that have overwintered, for periods of at least 9 months, between 1898 and 1958 have been assembled. Using a map of 1957–75 average annual temperature over Antarctica, the results for the expedition sites were made compatible with modern data. The expedition records are unfortunately confined mainly to two regions, the Antarctic Peninsula and the Ross Sea sectors. It is difficult, therefore, to generalize the results to the entire continental area. The expeditions are also somewhat irregularly spaced in time with relatively few occurring in the 1917–34 period. The best guess that can be made is that Antarctic air temperatures now appear to be warmer, by at least 1°C, than those prevailing during the first decade of the twentieth century. The result is broadly consistent with temperature changes that have been reported for both land and marine regions over the rest of the Southern Hemisphere. This result is, however, in contrast with the cou...

Comparing foreign subsidiaries and local firms in LDCS: Theoretical issues and empirical evidence

Abstract: The article reviews the empirical evidence on the comparative behaviour of foreign subsidiaries and locally‐owned firms in four main areas which have a bearing on development: technology, marketing, foreign trade and wages. It is argued that the conventional cross‐section analysis of the behaviour of the different types of firm is a poor guide to the impact of foreign investment on host countries, and that longitudinal industry studies are a more fruitful approach for future research.

To Risk or Not to Risk? Uses and Limitations of Mary Douglas on Risk-Acceptability for Understanding Health and Safety at Work and Road Accidents

Abstract: The recent Greening of politics in the West has encouraged rapid development of research into both environmental hazards and risk perceptions among the public. There are also longstanding traditions of research into behaviour under risk in such disparate fields as superpower relations (Allison 1971), inter-country commercial transactions, the economics of uncertainty, and the study of natural disasters (Torry 1979). Relatively few sociologists or social anthropologists have contributed. A major exception is Mary Douglas (1982, 1985, 1987). This paper is an attempt to make use of her work and to tests its limits, in answering two empirical questions: How do managers and workers address workplace hazards? And, how do motorcyclists and drivers behave on the roads?

Oligosaccharides that induce proteinase inhibitor activity in tomato plants cause depolarization of tomato leaf cells

Abstract: Two size ranges of oligosaccharide elicitors of pectic origin have been investigated for their effects on tomato plants. (...)

Global palaeoclimate of the late Cenozoic

Abstract: Preface to the Russian edition of Palaeoclimates of the Late Cenozoic by V.A. Zubakov and I.I. Borzenkova (Gidrometeoizdat, 1983). Preface to the Russian edition of The Global Climatic Events of the Pleistocene, by V.A. Zubakov (Gidrometeoizdat, 1986). PART I. THE GLOBAL CLIMATIC EVENTS OF THE PLEISTOCENE. Introduction. Section I. Methodological problems of palaeclimatology. 1. The time structure of climate. On the definitions of climate, palaeoclimate and palaeoclimatography. On the terms ``global climatic event'',``climathem'', climatostratigraphy. On the methods of high-resolution climatostratigraphic correlation and chronological scale of global climatic events. The principles of time classification of the global climatic events: Taxonomic differences in the climato - sedimentary cycles and climathems. The two climatic regimes in the history of the Earth. Main features of the glacial climatic regime. Main features of the greenhouse climatic regime. 2. Deep-sea standard for global climatic events. History of climatostratigraphic study of the Pleistocene. The significance of the oxygen-isotope scale for climatostratigraphic reconstructions. Systematic aspects of ``ocean-continent'' climatochronological correlation. The significance of geomagnetic data. Section II. Evidence for climatic changes in the Pleistocene - regional review. 3. Effects of global climatic events in the Mediterranean - Caspian system. The Mediterranean as a new climatoparastratotype region. The Caspian basin as a major record of changes in humidification in interior Eurasia. The Azov-Black Sea basin as a standard for the climatostratigraphic sequence on the shelf off Europe. The Mediterranean-Caspian paleohydrologic system as a record of global and regional climatic changes. 4. The loess assemblage of Eurasia as an indicator of climatic changes in the arid zone. The Loess zone of Europe. Loess in Asia. 5. Middle and high latitudes of the Northern Hemisphere as a major record of continental glaciation in Pleistocene time. Russian plain. Glaciated area in western and central Europe. West Siberia. North-eastern Asia and Beringia. North America. The Arctic and sub-Arctic. Section III. The history of climate through the Pleistocene. 6. On the timing of palaeoclimates in the Pleistocene. Debatable problems of inter-regional climatostratigraphic correlation. On correspondence between the numbrs of climathems on land and in the sea. On two stratific lines in the geo-historical classification of the Pleistocene. Comparison of experience in the long-distance stratigraphic correlation of the Pleistocene. Rhythm-chronological approach to the Pleistocene classification. On three types of time classification of the Pleistocene climatic events. The role of the 400 ka cycle for chronological classification of the Pleistocene. 7. Climatic changes in the Early and Middle Pleistocene. Introduction. The sixth (Gunz) kryo-superclimathem, 1.17-1.0 Ma.

Climatic change due to solar irradiance changes

Abstract: Solar irradiance reconstructions back to 1874 are used to estimate the effect of the Sun on global-mean temperature. The importance of the history effect, whereby recent temperature changes may be influenced significantly by past forcing changes, is evaluated. Modelled temperature changes are shown to be relatively insensitive to model uncertainties. The overall range of modelled temperature variations is extremely small, 0.05°C.