Showing papers by "University of East Anglia published in 1978"

Boulder shapes and grain‐size distributions of debris as indicators of transport paths through a glacier and till genesis

Abstract: Debris transported by glacier is derived either supraglacially from nunataks and valley sides or from erosion of the subglacial bed. Debris produced above the glacier by fracturing of rock walls has a dominant coarse fraction with angular boulders. Subsequent englacial or supraglacial transport is relatively passive and little comminution occurs. Debris eroded from subglacial bedrock is initially transported in a basal zone of traction, where particles frequently come into contact with the glacier bed and are retarded by it so that large forces may be generated between particles and the bed and at interparticle contacts. The material introduced into this tractional zone may be subglacial bedrock which has undergone a crushing-plucking event and which has a dominant coarse fraction, or supraglacially derived material which finds its way to the glacier bed. These parent debris assemblages are further comminuted by failure in response to locally concentrated compressive stresses, and attrition at shearing interfaces. Boulders transported through the tractional zone will tend to be rounded and bear several directions of striation. Large boulders embedded in lodgement till will tend to be streamlined with striae parallel to glacier flow and with an abruptly truncated distal extremity, rather like a roche moutonnee. Textural and boulder shape characteristics can be used to help distinguish different types of till.

Regulation of calcium fluxes and their regulatory roles in pancreatic islets

Abstract: It is today considered as crystal clear that calcium plays an essential role in the regulation of insulin release by the pancreatic B-cell. Some of the major issues concerning such a role are as follows: ( i ) what is the detailed mechanism by which secretagogues are susceptible to influence the handling of calcium in the B-cell; (ii) what is the nature and location of the critical pool of calcium that controls insulin release; (iii) what is the relative and respective contribution of calcium influx, efflux, and subcellar distribution in the regulation of such a pool; and (iv) how does calcium influence the process by which secretory granules migrate to the cell boundary and are extruded via exocytosis in the interstitial fluid.’ In the present report, for the sake of clarity, we will restrict the discussion of these questions to the process of glucose-induced insulin release, with the main emphasis on the possible significance of passive ionophoretic movements. The process by which glucose provokes insulin release can be viewed as a sequence of three major events, namely: ( i ) the recognition or identification of glucose by the B-cell; (ii) the subsequent remodelling of cationic fluxes; and (iii) the activation by calcium of an effector system controlling the migration and exocytosis of secretory granules.2 The role of calcium in insulin release is here considered within the framework of such a sequential view.

Determinate hydraulic geometry of river channels

Abstract: Natural channels have the ability to adjust their flow and bankfull hydraulic geometry in response to flow conditions. Nine governing equations are necessary to define the complete adjustment process and relate channel response to discharge, sediment load, bed, and bank sediment, and the valley slope. A preliminary analysis enables the nature of this process-response model to be identified although insufficient information is known about all the processes for it to be used for design purposes. The necessary dependent and independent variables for the development of empirical design equations are identified by the model and it also confirms the determinate nature of alluvial channels.

Some conditions which almost characterize Frobenius groups

Abstract: The main result of this paper is the following: LetG be a group with a proper non-trivial normal subgroupH such that each coset ofH distinct fromH is contained in a conjugacy class ofG. IfG is not a Frobenius group with kernelH then one ofH orG/H is ap-group. The hypothesis of this theorem is shown to be equivalent to a condition on characters ofG. The only group the author knows which satisfies this hypothesis and is not either Frobenius or ap-group is one of order 72.

Aspects of the ecology of Prymnesium parvum (Haptophyta) and water chemistry in the Norfolk Broads, England

Abstract: SUMMARY. Prymnesium parvum, an ichthyotoxic phytoplankter, has been recorded, at times abundantly, in the River Thurne, Norfolk, and its associated Broads. Its occurrence has been apparently more frequent and its population sizes probably larger since the late 1960s than previously and fish mortalities due to it now occur almost annually. The Thurne system is brackish and may have become more so, due to exploitation by drainage pumps, of a saline water table, in recent years. Evidence for this is conflicting, but in any case an increase in salinity is unlikely to have made increased Prymnesium growth more likely. Eutrophication of some Broads in the system is most likely to have increased the populations of Prymnesium since the late 1960s and data are presented on the present water chemistry of the system for comparison with previous records, and on current phytoplankton and Prymnesium crops in different parts of it. P. parvum has been isolated from the system as a unialgal culture and compared in morphology, salinity tolerance and ichthyotoxicity with a strain of P. parvum from Israel. The Broads strain differs slightly in size and pigmentation, but not in salinity tolerance. In culture it produces more ichthyotoxin than the Israeli strain.

Weather compilations as a source of data for the reconstruction of european climate during the medieval period

Abstract: Research into the climate of the Middle Ages has relied heavily upon data provided by compilations of references to weather and related phenomena extracted from a variety of historical texts and source documents. These compilations, produced from 1858 onwards, have generally neglected the essential need for source validation. While a considerable amount of reliable and useful information about medieval climate is to be found in documentary sources, it occurs together with material which is spurious, inaccurate, or whose reliability cannot be properly authenticated. Because they were, for the most part, scientists, unfamiliar with historical methodology and techniques of source analysis, the authors of the compilations were either unaware of the problematic character of their sources, or ignorant of the techniques developed by historians for dealing with them. The material included in the compilations must be regarded as suspect until its authenticity has been checked by validating individual sources. Unless this is done, a misleading picture of the climate of the Middle Ages may emerge from uncritical use of the compilations. In particular, the climate may appear to have been more extreme than authentic sources alone would suggest.

Palaeoclimatic and geomorphic implications of 230 Th/ 234 U dates on speleothems from Britain

Abstract: A priori arguments and empirical evidence both suggest that widespread deposition of calcite in caves takes place in non-glacial climatic conditions. Radiometric dates from calcite speleothems in Britain indicate deposition before 170,000 yr b.p., during an interglacial around 90–140,000 yr b.p., an inter stadial at 60,000 yr b.p. and in the late Devensian and Holocene. The positions of speleothems within caves allow minimum ages to be estimated for past water tables and associated surface landforms. The main erosion of the Yorkshire Dales is shown to date from before 400,000 yr b.p., while Cheddar Gorge in the Mendip Hills has been deepened by 70 m during the last 400 millenia.

Cis-heptadeca-1,9-diene-4,6-diyne-3,8-diol, an antifungal polyacetylene from carrot root tissue

Abstract: A compound isolated from root tissue extracts of Daucus carota L. showed antifungal activity towards Mycocentrospora acerina and Cladosporium cladosporioides . It was identified with the aid of u.v. and infrared spectroscopy, nuclear magnetic resonance and mass spectrometry as cis -heptadeca-1,9-diene-4,6-diyne-3,8-diol with the trivial name of falcarindiol. A concentration gradient in carrot roots varying from 93 μg/g fresh wt in periderm and pericyclic parenchyma to 2 μg/g in xylem parenchyma was demostrated. The ED 50 for inhibition of germination of chlamydospores of M. acerina was 31·8 μg/ml. The role of this compound in disease resistance is discussed.

Holocene palaeo-wind evidence from palynology in Baffin Island

Abstract: TRACE amounts of wind-blown tree pollen from the highly productive boreal coniferous forests are a characteristic component of arctic tundra sediments1,2. These exotic pollen are generally regarded as mere contamination or distractions in tundra pollen diagrams3. We report here that traces of exotic pollen in late Holocene sediments from Baffin Island can be used as palaeo-wind indicators, and may be associated with periodic shifts of a trough in the atmosphere.

The Theory of the Spatial Diffusion of Innovations: A Spacious Cul-De-Sac:

Abstract: This article critically reviews the progress that has been made in the spatial diffusion theory of innovations, particularly since the last review in Progress in Geography (Brown arid Moore, 1969). Such an undertaking prompts two related questions-progress for whom, and by what criteria do we judge ‘progress’? Almost all social sciences have been undergoing an increasing degree of self-examination and criticism, whereby the ‘half-life’ of theories and paradigms has consistently become shorter-partly due to the increasing output of research itself, and to changes in the world political economy. Geography has been a part of this process, although the impulses have usually been transmitted from without, and received and reinterpreted by practitioners within. There are two reasons for this which concern the nature of space itself as well as the nature of those who study it. First, space is precisely what the political economy makes it; second, the way in which space is studied is inherently ideological. To take the first proposition, it is clear that space in human geography implies relationships between man and ‘nature’ and man and man. Since man usually enters into social relations of producti6n in order to earn a livelihood and reproduce himself, spatial relations are derived from and defined by production relations. Indeed how ‘nature’ is defined and how men relate to each other is a result of the mode of production itself (natural resources are not, they become). Thus ‘geographers are belatedly realizing that man’s organization of space and use of environments reflects his social organization’ Uohnston, 1976). Criteria for evaluating progress and the nature of space

Amino Acid Recycling in Relation to Protein Turnover

Abstract: Methods of measuring amino acid recycling in Lemna minor are described. The extent to which the recycling of individual amino acids may underestimate protein turnover has been measured for a number of amino acids. The methods have been used to study the relationship between protein turnover and amino acid recycling during nitrogen starvation. It is concluded that following the removal of nitrate from the environment, protein turnover is enhanced, the partitioning of amino acids between protein synthesis and amino acid metabolism is relatively constant, but the total amount of amino acids recycling is increased.

Limitation of gaeumannomyces graminis by wheat root responses to phialophora radicicola

Abstract: SUMMARY Changes in wheat roots invaded by Phialophora radicicola var. graminicola, P. radicicola var. radicicola and Gaeumannomyces graminis var. tritici were explored. Progress of Phialophora radicicola var. graminicola was arrested by lignitubers in the third cortical layer whereas P. radicicola var. radicicola progressed as far as the innermost layer of the cortex, failing to penetrate the endodermis, but was not arrested by detectable structural changes. Both varieties of P. radicicola elicited considerable lignification of the stelar components, and lignification and suberization of the inner tangential wall of the endodermis. When the two species of fungi were inoculated on the same root, P. radicicola var. graminicola prevented Gaeumannomyces graminis var. tritici from spreading longitudinally in the stele.

Genesis of the Skagit Gneiss migmatites, Washington, and the distinction between possible mechanisms of migmatization

Abstract: Some possible chemical and morphological criteria to distinguish different migmatization mechanisms are considered and examples of the different processes discussed Leucosomes formed by anatexis are likely to contain K-feldspar and should have a more sodic plagioclase than the restite rocks Metamorphic segregation can cause a slight fractionation of albite into the leucosome only Anatectic leucosomes might form irregular bodies or might agmatize the restite; close-spaced planar veins are improbable Leucosome veins formed by hydrothermal processes are likely to be coarse grained or pegmatitic, whereas water-rich anatectic melts may freeze readily to aplites The criteria developed are applied to the Skagit Gneiss migmatites, and although the temperature of metamorphism was high (<700 °C), an anatectic model is rejected, as in earlier studies Much of the migmatization that accompanied regional deformation and metamorphism was due to metamorphic segregation Many other leucosomes are believed to be related to an extensive suite of plagioclase pegmatite dikes, probably of hydrothermal origin, that were emplaced at a late stage These dikes are of uniform composition (plagioclase ≃ An20), irrespective of the host rock, and the plagioclases of some feldspathized schists tend toward this composition Recent fluid-inclusion studies have shown that high-grade rocks have a mixed CO2-H2O fluid Therefore, partial melting is unlikely to begin until temperatures well in excess of the water-saturated granite solidus are reached Melts so formed might readily coalesce and migrate out of the source rock without producing an extensive migmatite zone Many migmatite terranes may have formed by predominantly hydrothermal processes, notably metamorphic segregation, and it is possible that this might represent a particular type of tectonic environment

“Dew” as a sink for sulphur dioxide

Abstract: Calculations suggest that transfer of SO 2 into leaf wetness (“dew”) is relatively rapid and it should remain in equilibrium with the atmosphere. The volume of leaf wetness appears to be insufficient to absorb more than 0.3 % of the SO 2 emitted in the U.K. each year unless it is neutralized by alkaline materials such as ammonia. Analysis of leaf wetness in winter at a semi-rural site gave SO 2- 4 as 1.06 ± 0.56 times 10 ?4 mol l ?1 which places the maximum deposition into “dew” over the U.K. at 0.12 Mtonne yr ?1 (2.3 % of emissions). DOI: 10.1111/j.2153-3490.1978.tb00828.x

Climatic signals in British Isles tree-ring chronologies

Abstract: INTERPRETATION of proxy records of past environmental conditions derived from dated geological or biological materials is of great importance for the extension of the climatic record1,2. Precisely dated, replicated tree-ring series have been particularly useful as they provide records (usually ring-widths) dated to the individual year, for hundreds or thousands of years. Each such series, or chronology, is derived from a particular known location. Thus a network of such chronologies may be developed for a particular region and used as a proxy record of spatial and temporal climatic variations. This has been achieved in North America by Fritts et al.3,4, using principally chronologies from semi-arid areas or from near altitudinal or polar tree-lines. We report evidence here that tree-ring chronologies from sites in the British Isles will provide suitable proxy records for the reconstruction of historical temporal and spatial variation of climate.

Localised chiasmata due to partial pairing: A 3D reconstruction of synaptonemal complexes in male Stethophyma grossum

Abstract: The possible role of localised pairing as a mechanism producing localised chiasmata in Stethophyma grossum spermatocytes has been examined ultrastructurally. Nuclei at four successive stages of meiosis from leptotene to pachytene were reconstructed from a series of ultrathin sections and the extent of synapsis as demonstrated by synaptonemal complex (SC) formation was calculated. On the basis of the relative lengths of SCs and condensed chromosomes it was reasoned that only the centromeric ends of the long and medium length bivalents paired, and only one end of these SCs was found attached to the nuclear envelope. Only the three shortest bivalents paired completely, and both their SC ends were attached to the nuclear envelope. Thus pairing was directly related to the distribution of chiasmata. The extent of pairing at different stages suggests that the shortest bivalent paired very quickly, the longer ones progressively slower, and that pairing proceeded zip-like from a point at or very close to the end attached to the nuclear envelope, since all stretches of SC were attached to the envelope, and there were never more than 11 pieces, one for each bivalent. Chromosome decondensation and axial core formation did not occur far in advance of SC formation, and synapsis appeared to be much slower in S. grossum than in other species with non-localised chiasmata, as a larger proportion of the meiotic cysts were in “zygotene”, compared to Stauroderus scalaris and Locusta migratoria, although this was not quantified.

The reaction of Pseudomonas aeruginosa cytochrome c-551 oxidase with oxygen.

Abstract: The reaction of ascorbate-reduced Pseudomonas cytochrome oxidase with oxygen was studied by using stopped-flow techniques at pH 7.0 and 25 degrees C. The observed time courses were complex, the reaction consisting of three phases. Of these, only the fastest process, with a second-order rate constant of 3.3 X 10(4) M-1.S-1, was dependent on oxygen concentration. The two slower processes were first-order reactions with rates of 1.0 +/- 0.4s-1 and 0.1 +/- 0.03s-1. A kinetic titration experiment revealed that the enzyme had a relatively low affinity constant for oxygen, approx. 10(4)M-1. Kinetic difference spectra were determined for all three reaction phases, showing each to have different characteristics. The fast-phase difference spectrum showed that changes occurred at both the haem c and haem d1 components of the enzyme during this process. These changes were consistent with the haem c becoming oxidized, but with the haem d1 assuming a form that did not correspond to the normal oxidized state, a situation that was not restored even after the second kinetic phase, which reflected further changes in the haem d1 component. The results are discussed in terms of a kinetic scheme.

Quenching of triplet states of aromatic ketones by indole and 3‐methyl indole in benzene solution. evidence for hydrogen‐atom abstraction, for quenching due to favourable charge transfer interaction and for the lack of electronic energy transfer

Abstract: — Quenching of the triplet states of the aromatic ketones (KCO), benzophenone, acetophenone and xanthone, by indole and 3-methyl indole gives rise to the neutral radicals resulting from hydrogenatom transfer with variable efficiency (40–100%). Thus in addition to the reaction, 3KCO*+RH KCOH +R. some other quenching path or paths occur. There is no evidence for any triplet energy transfer even when this is energetically favourable, and it is suggested therefore that quenching to give ground state species following favourable charge-transfer interactions accounts for the proportion of quenching without reaction. The spectra of the indole radicals, R., were determined and the kinetics of their decay in aerated and deaerated solution were investigated and reaction schemes proposed to explain these observations.

Investigation of the Interaction of Triethyltin with Rat Liver Mitochondria Using Binding Studies and Mössbauer Spectroscopy

Abstract: 1 The binding of triethyltin to rat liver mitochondria is measured and the results indicate the presence of a three component system. This involves triethyltin binding to two specific sites, one of high affinity, which is found to have a concentration similar to that found for the F1-ATPase complex and one of lower affinity. The third component is attributed to partition of triethyltin into the mitochondrial membrane. 2 Non-specific partition is shown by inhibition of triethyltin binding to the low affinity site with N-ethylmaleimide and to the high affinity site by buffer pH values lower than pH 5.7. Combination of these two conditions leaves a Scatchard plot which can be interpreted as being due to triethyltin partitioned into the mitochondrial membrane. 3 The selective inhibition of triethyltin binding to the low affinity site by N-ethylmaleimide preincubation indicates the presence of a thiol group in the low affinity site and the absence of N-ethylmaleimide-reactive thiol groups necessary for triethyltin binding in the high affinity site. 4 Mossbauer spectra of triethyltin bound to mitochondria also seem to be derived from the same three component system. N-Ethylmaleimide preincubation assigns an absorption doublet to low affinity bound triethyltin and the concentration dependence of the absorption intensities assigns a second doublet to partitioned triethyltin. 5 Washing triethyltin pretreated mitochondria leaves an absorption doublet which is assigned to high affinity bound triethyltin. This assignment is confirmed by binding and ATPase activity studies before and after this washing procedure. 6 Triethyltin bound to the high and low affinity sites is found, by the ratio of the Mossbauer quadrupole splitting and the isomer shift obtained, to be four coordinate or possibly cis-five coordinate. 7 The assignment of the absorption doublet, from triethyltin in the high affinity site environment, to a four coordinated triethyltin-mitochondrial membrane complex is suggested by the investigation of some intramolecularly coordinated triorganotin compounds.

Machine translation and machine‐aided translation

Abstract: The recent report for the Commission of the European Communities on current multilingual activities in the field of scientific and technical information and the 1977 conference on the same theme both included substantial sections on operational and experimental machine translation systems, and in its Plan of action the Commission announced its intention to introduce an operational machine translation system into its departments and to support research projects on machine translation. This revival of interest in machine translation may well have surprised many who have tended in recent years to dismiss it as one of the ‘great failures’ of scientific research. What has changed? What grounds are there now for optimism about machine translation? Or is it still a ‘utopian dream’ ? The aim of this review is to give a general picture of present activities which may help readers to reach their own conclusions. After a sketch of the historical background and general aims (section I), it describes operational and experimental machine translation systems of recent years (section II), it continues with descriptions of interactive (man‐machine) systems and machine‐assisted translation (section III), (and it concludes with a general survey of present problems and future possibilities section IV).