Showing papers by "University of Exeter published in 1979"

The Assessment of Prostatic Obstruction from Urodynamic Measurements and from Residual Urine

Abstract: One hundred and seventeen males over the age of 55 were investigated for possible prostatic obstruction. About half of the cases in this series could have been objectively classified as unobstructed or obstructed from the maximum flow rate alone. In about two-thirds of the cases obstruction could be satisfactorily assessed from the maximum flow rate together with the detrusor pressure at maximum flow. It was not helpful to combine these 2 measurements into a single urethral resistance factor. In the remaining one-third of the cases, obstruction could be objectively assessed only from a plot of detrusor pressure against flow rate throughout micturition. In many of these cases both the pressure and the flow rate were low and the main peculiarity was that the contractile power of the bladder was weak. Residual urine is a sign of an abnormality of bladder function rather than the direct result of urethral obstruction.

The effects of collembola grazing on microbial activity in decomposing leaf litter

Abstract: Ground leaf litter was inoculated with the fungus Coriolus versicolor and incubated in respirometers for 6 days (“fresh” cultures) or 33 days (“senescent” cultures) before different number of Folsomia candida were added. Grazing by 5 animals stimulated O2 consumption in both series of cultures but 10, 15 or 20 animals inhibited microbial respiration. The stimulatory effect was less marked in the senescent cultures. Bacterial and fungal standing crops increased in “fresh” cultures during the course of the experiment but grazing by collembola increased bacterial and reduced fungal standing, crops in proportion to the grazing intensity. Microbial standing crops were not determined for senescent cultures. Microarthropod feeding activities can therefore exert a strong differential effect on fungal and bacterial populations which has not been previously recognised.

The structure of smectic A phases of compounds with cyano end groups

Abstract: 2014 The smectic layer spacings (d) have been determined for a number of cyano derivatives which have an anomalous d/l ratio of ~ 1.4, where l is the molecular length. It is shown that the quantity (d 2014 l) is directly related to the length of the alkyl or alkoxy tail of the molecule but is not simply related to the length of the aromatic core. This is consistent with a bimolecular layer structure having overlapping molecular cores at the layer centre. Using a combination of X-ray and neutron diffraction measurements of the intensity of the layer reflections on several isotopically substituted forms we have positively confirmed and quantified this model for one compound (4-cyano4’-n-octylbiphenyl, 8CB). LE JOURNAL DE PHYSIQUE TOME 40, AVRIL 1979, Classification Physics A bstracts 61. 30

Photosynthesis, respiration and water content in bryophytes

Abstract: Summary Response curves of photosynthesis to water content of bryophytes of dry habitats (e.g. Tortula intermedia, Camptothecium lutescens) show an optimum, with photosynthesis declining again at high water contents. Respiration may be stimulated by water stress, but is unaffected by high water contents. The steep portions of the photosynthesis and respiration curves lie within a similar range at low water contents. Some species of constantly moist habitats (e.g. Pellia epiphylla, Hookeria lucens) show photosynthesis increasing progressively to water contents of 500 to 1000 % of dry weight, and affected at much lower water deficits than respiration as the plant dries out. The response of photosynthesis and respiration to water potential is broadly similar in the two groups. In the species investigated there was generally measurable photosynthesis at –60 to – 100 bar, but little or none at – 150 to –200 bar. Respiration continues to somewhat lower water potentials of which the limits were not determined. Field measurements of the water content of shoots of five species over a period of 12 months showed much greater variation in Tortula muralis than in the woodland species. Maximum water contents in the field generally lay close to the optima of the photosynthesis response curves. The lower water contents recorded in these and in published data are considered in relation to sorption isotherms for bryophytes and other plant materials. The water associated with bryophyte shoots can be divided into (1) water within the cell walls (apoplast water), (2) water within the cytoplasm (symplast water), and (3) external capillary water. Changes in water content below about –200 bar take place chiefly within (1), between c.– 200 and c. - 2 bar within (2), and at higher water potentials chiefly within (3). Water movement within the shoots is physiologically important; the distribution and movement of water are mediated by the geometry of the capillary spaces of the cell walls and the plant surface. In species with papillose leaves, rates of capillary conduction in the interstices between the papillae are more than sufficient to balance evaporation. Conduction within the cell walls is likely to be important in species with non-papillose leaves, hut other pathways may also be involved, and water movement in these species requires further investigation.

Distribution functions in three liquid crystals from X-ray diffraction measurements

Abstract: The intensities of X-ray scattering from three compounds has been measured photographically at a number of temperatures. The substances studied were 4,4′di-n-octyloxyazoxybenzene (OOAB) and its di-n-heptyl homologue (HOAB) in their nematic and smectic C phases and ethyl-4-(4′acetoxybenzylidene)aminocinnamate (EABAC) in its nematic and smectic A phases. In all cases except the smectic C phase of HOAB the distribution function f d(β) describing the orientation of the local director for clusters of ≳ 10 molecules relative to the average director has been determined. The form of f d(β) is close to that predicted by simple mean field theory although the magnitude of the order parameters ⟨P 2⟩ in general differ significantly. from the simple mean field values. The results suggest that f d(β) is close to the true singlet distribution so that the dominant angular fluctuations are co-operative and involve several molecules. For the smectic phases properties of the density wave f(z) which is the smectic layer distr...

Function, homology and terminology in insect wings

Abstract: . The history of current systems of wing nomenclature is summarized, and the underlying principles reviewed. The homologies of wing areas are clarified, with particular reference to the functions and positions of longitudinal lines of bending in the wings. Distinction is drawn between flexion-lines, primarily aerodynamic in function, and fold-lines, which are primarily concerned with wing-folding. Of these the claval furrow - a flexion-line - and the jugal fold-line are, when recognizable, nearly constant in position, and are hence valid area boundaries and useful landmarks in vein identification. The vannal fold-line and the median flexion-line are variable in position, and hence unsatisfactory area boundaries. The nature and functioning of fold- and flexion-lines in the axilla of Locusta are described and illustrated, and names are proposed. Conflicting aspects of commonly-used systems of wing terminology are evaluated; and illustrated recommendations are put forward for consistent naming of veins, branches and wing areas.

Suspended sediment sources identified by magnetic measurements

Abstract: A procedure for identifying the main source of the suspended sediment load of a stream by simple, cheap, rapid and nondestructive magnetic measurements is applicable to samples taken during the routine sampling of flood events permitting general characterisation of the load and more detailed investigation of variations in sediment source both during and between individual flood events.

Molecular dynamics of liquids modelled by '2-Lennard-Jones centres' pair potentials

Abstract: The molecular dynamics study based on two-Lennard-Jones (12-6) centres pair potentials, with reduced bond lengths in the range 0·5 ⩽l/σ⩽0[sbreve]d8, and with e, σ-parameters simulating liquid F2, Cl2, Br2 and CO2 (14) is extended to time correlation functions. The calculated properties include: translational velocity and force self correlation functions; orientational self-correlation functions , a cross correlation function for P 2, angular momentum (J), and torque self-correlation functions. Diffusion constants (D) and rotational relaxation times (τ1, τ2, τ J ) have been evaluated and where possible compared with experimental data (D and τ J for F2, τ2 for Cl2). Calculations with 108 or 256 molecules are reported for several densities and temperatures for four model liquids. The nature of the one-particle motion is analysed qualitatively in terms of quasi-oscillations and -librations. It is difficult to fit the observed features into the framework of physical models proposed in the lite...

The influence of fungal food quality on the growth and fecundity of Folsomia candida (Collembola: Isotomidae).

Abstract: The Basidiomycete fungi Coriolus versicolor and Hypholoma fasciculare were grown in liquid media containing 2, 20, 200 and 2,000 ppm nitrogen (as asparagine) and fed to cultures of Folsomia candida. Collembola feeding on both species of fungi exhibited trends of increased moulting and egg laying rates up to 200 ppm N and an inhibition of growth and fecundity at 2,000 ppm N. The differences in moulting rates between individual treatments were small for both species of fungi and not all the pair wise comparisons of treatments were significantly different. Egg laying rates of collembola fed C. versicolor showed a highly significant response to all levels of N in the growth medium and egg production at 200 ppm N was over three times higher than at 2 ppm N. Collembola fed H. fasciculare showed a less marked fecundity response to the different nitrogen levels and egg production at 200 ppm was approximately 1.5 times higher than at 2 ppm N. Both moulting and egg laying rates were significantly affected by the species of fungus presented as food to the collembola. The patterns of growth and reproduction of starved control groups of F. candida as well as those fed the test fungi demonstrate the adaptability of this species to changes in the quality and quantity of available food.

The occurrence and natural alleviation of stunting in a population of roach, Rutilus rutilus (L.)

Abstract: Two sudden and pronounced changes in the growth rate of roach, Rutilus rutilus (L.), in Slapton Ley, Devon, have been observed between 1972 and 1976. At first the growth rate declined to the point at which the population became stunted, then subsequently it improved again. These changes were correlated with population density; the numbers of roach were increasing during the late 1960's/early 1970's, and this increase was substantially reinforced by very strong year classes in 1972, and, to a lesser extent, in 1973. The increase in population density resulting from the strong 1972 year class was apparently adequate to accelerate the onset of the stunting observed. The improvement in growth rate in 1976 followed immediately after extensive mortalities amongst the roach during 1975, caused by an epidemic of the parasite Ligula intestinal is (L.). Some improvement in the growth of O group roach had been evident during 1975, but this was not observed in the population. Ford-Walford plots showed a decline in the value of L after the onset of stunting in 1972. Differences in the reproductive biology of the fish were found following the alleviation of stunting; the gonads of both sexes achieved a greater relative weight, and correspondingly the fecundity of the females was higher, although this latter effect became progressively less marked with increasing size. It was not apparent amongst the largest individuals. There was also some evidence of a decline in the proportion of fish maturing at minimum size. The changes in the reproductive biology were associated with the improvement in conditions for individual fish following the decline in population density.

The structure of vapour-deposited arsenic sulphides

Abstract: High resolution X-ray and neutron correlation functions have been obtained for arsenic sulphide bulk glass and vapour-deposited films by making measurements to high momentum transfers. These data are compared with a vatiety of models and it is concluded that the structure of the films is dominated by the presence of As4S4 molecules in the vapour phase, which results in more As-As bonds than the minimum required by stoichoimetry. The extent to which these As4S4 molecules polymerise in the as-deposited film is unclear, but depends strongly on preparation conditions.

Colonization of wood blocks by aquatic hyphomycetes

Abstract: Oak wood blocks of graded sizes were submerged in a stream to study their colonization by aquatic hyphomycetes. Three times as many species were found on the largest blocks as on the smallest ones. Six species were found on blocks of all sizes, a further seven species were present on all but the smallest blocks and another six species were found occasionally on the largest blocks only. These results indicate that the species composition of aquatic hyphomycete communities is closely related to the size of the available resources and that other species may be excluded once a species assemblage is established.

The mechanism of microtubule associated cytoplasmic transport. Isolation and preliminary characterisation of a microtubule transport system.

Abstract: The nutritive tubes of telotrophic insect ovaries are cytoplasmic channels along which ribosomes are transported over distances of several mm from trophic cells to the developing oocytes. The presence within the nutritive tubes of a massive number of orientated microtubules renders them strongly birefringent in polarised light, a property which, together with their size, rendered them amenable to isolation by microdissection. Ultrastructurally the isolated tubes were indistinguishable from undissected controls. Polyacrylamide gels revealed a consistent pattern of some 30 bands of which tubulin was the most prominent. The tubes also contained a band which comigrated with the major high molecular weight micro tubule associated protein (MAP) from mouse brain but no detectable actin, myosin or dynein. Microtubules in the isolated tubes were not depolymerised by treatments (cold, calcium and colchicine) which typically disrupt cytoplasmic microtubules. Following extraction of the membrane enclosing the tubes and the cytoplasmic matrix the microtubule cytoskeleton persisted, retaining its cylindrical organisation although no bridges between the microtubules were detected in the electron microscope. The possibility that the stability and spatial deployment of the nutritive tube microtubules is conferred by specific microtubule accessory proteins is discussed.

Interlayer correlations in smectic B phases

Abstract: 2014 X-ray diffraction results are presented on very well aligned samples of several smectic B phases which show the existence of several kinds of interlayer correlations. The hexagonal closepacked layers may be stacked with ordered ABA... or ABCA... arrangements (where A, B and C denote the relative position of the layers), with a random array of ABC-type planes, or with almost no correlation between layers. No clear examples of the simple monolayer packing AA... have been found. LE JOURNAL DE PHYSIQUE LETTRES TOME 40, 15 JUILLET 1979,

Association of Actinomycete-Like Bacteria with Soil-Feeding Termites (Termitidae, Termitinae)

Abstract: Electron microscopy of the hindgut showed that actinomycete-like bacteria were the principal microbial associates of two African species of soil-feeding termites. Elongated cuticular spines provided attachment.

Student Teacher Anxiety and Class-Control Problems on Teaching Practice: a cross-lagged panel analysis

Abstract: Summary The anxiety about teaching of 100 PGCE students was measured both near to the beginning and to the end of a term's teaching practice. A significant decrease in anxiety was found which was essentially the same for all the subgroups based on male/female and science/non-science divisions. A cross-lagged panel analysis provided some indication that for the student teachers of science, but not for the teachers of non-science subjects, anxiety was a cause, rather than a consequence, of class-control problems. Such a result had been hypothesised in the light of a model of teacher behaviour based upon catastrophe theory.

Civic Humanism and Parliamentary Reform: The Case of the Society of the Friends of the People

Abstract: The tradition of thought known as civic humanism has recently occupied the attention of a number of commentators. Not only has it been examined in the place of its birth, Renaissance Italy, and more especially Florence, but in a recent work J. G. A. Pocock has traced the influence of the tradition in seventeenth and eighteenth-century England, and finally in the New World. The question considered here is the particular use to which civic modes of thought and argument were put by a group of moderate reformers in the debates on parliamentary reform in the last two decades of the eighteenth century. Although this period has received attention from social and constitutional historians, it has not been discussed by historians of ideas.Civic humanism is both an analysis of a political problem and a range of recommendations as to how the problem is best to be solved. The problem is defined in terms of the deleterious effects of time on political organization. Human organizations rely on the ordered and rule-governed behavior of individuals. Such behavior exhibits, over time, a constant tendency to disintegrate into selfish action. Political and legal institutions provide the immediate incentives to prevent this happening. Yet how can these institutions themselves be safeguarded or rendered self-regulating?The solution to the problem of achieving political stability through time is seen essentially as a moral solution, that is to say it is seen to lie in the creation of a particular set of attitudes towards political life amongst the citizens of the polity.

The role of natural convection mass transfer in the kinetics of electropolishing of horizontal surfaces

Abstract: Limiting currents were measured for the electropolishing of horizontal copper electrodes facing downwards in phosphoric acid solution under natural convection conditions. The electrode diameter was varied from 1–6 cm and the phosphoric acid concentration between 8–12 M. The limiting current was found initially to decrease with electrode diameter and then to remain constant with further increase. Within the concentration range of phosphoric acid used, the limiting current was found to decrease with phosphoric acid concentration. Mass transfer data was found to agree closely with the equation $$(Sh) = 0 \cdot 18[(Sc)(Gr)]^{0 \cdot 33} for 1 \cdot 1 \times 10^9< (Sc)(Gr)< 2 \cdot 46 \times 10^{11} .$$

Interspecific dominance amongst three species of coarse fish in Slapton Ley, Devon

Abstract: Marked changes in the relative numbers of roach Rutilus rulilus (L.), rudd Scardinius erylhroplhalmus (L.) and perch Perca fIuviatilis L., in Slapton Ley, Devon, have been observed over the period 1967–1978. Historically, the lake had been dominated by rudd and perch; significant numbers of roach were not thought to be present until 1967. From then onwards the roach population exhibited a considerable expansion, apparently replacing the rudd, which had virtually disappeared by 1974. In 1975 extensive mortalities of roach were caused by the pseudophyllidean cestode Ligula intestinalis L. During 1976 and 1977 larger number of rudd, belonging to the 1975 and 1976 year classes, were present, suggesting that the roach mortalities might be giving the rudd a chance to recover. However, very few rudd were present during 1978, possibly because lower incidences of ligulosis during 1976–1978 had allowed the roach to recover from the main outbreak of the disease in 1975, and to replace the rudd for the second time. Evidence from trap catches indicated that the perch population had shown a consistent decline between 1970 and 1977. The major phase of this decrease occurred between 1971 and 1973, when the roach population was increasing the most rapidly. Comparisons were made with changes in fish populations in other localities. The major reason for the changes observed was thought to be a competitive relationship between the plankton feeding younger stages, with roach being the dominant species, although other factors may also have been involved.

The social aetiology of disasters

Abstract: When disasters were seen as infrequent destructive events arising from the influence of remote cosmic forces, it made little sense to spend any length of time in considering these causes, since not only were the events themselves so infrequent and idiosyncratic in their incidence as to be unlikely to yield useful generalisations, but they were also likely to arise from inherently inscrutable and uncontrollable sources. The best that could be done was to concentrate upon the provision of rescue and relief services when these were required, in order to treat the symptoms rather than the causes of disaster. This situation has been changing, however, in a number of ways. World-wide communications have developed, so that we are now more aware than isolated local communities could have been in the past of similar kinds of events recurring at slightly different locations. At the same time, our growing understanding of the nature of our environment bas been leading us to realise that many destructive natur phenomena

A study of the home ranges of free-ranging Exmoor ponies

Abstract: The ecology of the free-ranging Exmoor ponies has not previously been studied. In this investigation, the locations of the few pure-bred herds are given, together with information on their populations, and the reasons for selecting the Withypool Common herds are outlined. The features of this main study area, the types of ponies and their special groupings are described in some detail. The home ranges of the Exmoor herds are examined on an annual and monthly basis, and their relationships to each other and to that of the mongrel herd are studied. This is followed by information on the changing patterns of the two Exmoor pony ranges and a discussion of the significance of inter-stallion relationships. Finally, the home range systems are assessed for features of territoriality.