Showing papers by "University of Exeter published in 1977"

Thermodynamic and structural properties of liquids modelled by ‘2-Lennard-Jones centres’ pair potentials

Abstract: Molecular dynamics calculations have been carried out for model liquid systems of N (=108 or 256) molecules interacting through two Lennard-Jones (12–6) centres coinciding with the positions of the atomic masses (the ‘atom-atom’ pair potential). The objectives were (a) to study the dependence of the properties on the molecular anisotropy defined by the reduced distance l*=l/σ between the centres in the range 0·5–0·8; and (b) to compare the computed quantities with those of real liquids (F2, Cl2, Br2, CO2). This paper deals with thermodynamic and structural features. Time-dependent correlations will be treated in a future communication. In the liquid region not too far from the triple point the energy and pressure isochores are well represented by straight lines, the slopes of which increase with density and anisotropy. Thermodynamically consistent expressions for the energy and pressure as functions of density and temperature have been obtained for each system. With Lennard-Jones parameters adjusted so as...

Demand for food on fixed-ratio schedules as a function of the quality of concurrently available reinforcement1

Abstract: Six rats lever pressed for food on concurrent fixed-ratio schedules, in a two-compartment chamber. In one compartment, mixed diet pellets were delivered on fixed-ratio schedules of 1, 6, 11, and 16; in the other, either no food was delivered, or sucrose or mixed diet pellets were delivered on fixed-ratio 8. The number of pellets obtained in the first compartment declined as a function of fixed-ratio size in that compartment in all three conditions, but the decline was greatest overall with mixed diet pellets concurrently available in the other compartment, and least with no food concurrently available. The result is discussed in terms of economic demand theory, and is consistent with the prediction that elasticity of demand for a commodity (defined in operant terms as the ratio of the proportionate change in number of reinforcements per session to the proportionate change in fixed-ratio size) is greater the more substitutable for that commodity are any concurrently available commodities.

Urodynamic assessment of bladder function.

Abstract: Bladder function in micturition may be studied, without interference from the urethra, through 2 parameters, Piso and Q, which are measures respectively of the maximum pressure and of the maximum flow rate that the bladder can generate, i.e. of its intrinsic strength and speed. These parameters may be determined in a standard urodynamic investigation if the patient interrupts voiding for a short time with the external sphincter. The normal ranges of Piso and Q depend only slightly on age and sex and seem to be as follows: Piso, 50 to 100(+)cm H2O in both sexes; Q, 35 to 120 ml s-1 in males, 20 to 80 ml s-1 in females. There are significant differences in both parameters between different groups of patients. Many females, with stress or urge incontinence or with urgency, have bladders which seem to be weaker than normal (low Piso). The majority of proximally obstructed males, and many who have been surgically relieved of obstruction, have bladders which are significantly slower than normal but are of normal strength (low Q, normal Piso). Therefore the characteristic response of the detrusor to obstruction appears to be not the expected mechanical hypertrophy (Turner Warwick et al., 1973) but reduction in intrinsic speed. In contrast, a few proximally obstructed males and most males with a history of primary enuresis (persisting after 6 years of age) have bladders of normal speed and of strength significantly greater than normal (normal Q, high Piso), suggesting true mechanical hypertrophy of the detrusor. Females with a history of primary enuresis do not show this pattern so clearly. Since these sex- and disease-related differences must surely be of clinical significance, and since it is so easy to measure Piso and Q by the method given in section (e) of the Appendix, those who are concerned with clinical urodynamics are urged to investigate bladder function in this or some equivalent way (e.g. that proposed by Schafer and Melchior (1975)).

Critique of the chitin assay technique for estimation of fungal biomass

Abstract: Colorimetric determination of chitin content of nine aero-aquatic hyphomycetes showed that the conversion factor (CF) values (chitin content per unit dry weight of mycelium) varied with the age of mycelium, nutrient content of the medium, and initial oxygen concentration of the water. CF values often decreased with age of mycelium and also with lowered oxygen concentrations. Consequently, for estimation of fungal biomass in tissues, this technique is of limited value.

A comparison of the structures of vapour-deposited and bulk arsenic sulphide glasses

Abstract: Accurate comparative measurements have been made of the X-ray diffraction pattern of a bulk arsenic sulphide glass prepared from the melt and a 250 μm film prepared by vapour deposition of the evaporated bulk. By using Ag Kα radiation, measurements have been made up to Q = 21 A −1 (Q = 4π sin θ/λ) so as to give good spatial resolution. Significant differences are found between bulk and film specimens, and in particular a shoulder is found on the high r side of the first peak in the distribution function for the film. Also, the film is richer in arsenic than the parent bulk. The results are compared in detail with a number of models, all of which involve covalent bonding requirements being fully satisfied, and it is concluded that there are more AsAs bonds in the film than the minimum required by stoichiometry and that a significant fraction ( ≈ 2 3 ) of these are unusually long ( ≈2.6 A compared to the more usual 2.5 A). The most probable explanation is that the vapour contains a significant fraction of As4S4 species (in which the AsAs distances are ≈2.6 A ) and that the film contains a mixture of molecular species which have undergone considerable polymerization. The extent to which this results in a sheet-like structure similar to that proposed for the bulk glass remains unclear.

Photosynthesis of Conifers in Relation to Annual Growth Cycles and Dry Matter Production

Abstract: Observations that deciduous and evergreen conifers growing in Britain show similar annual growth increments, despite marked differences in short-term growth rates, led to a comparative study of seasonal photosynthetic capacity in established trees of four coniferous species with contrasting growth habits. The photo-synthetic data were compared with seasonal changes in environmental parameters and chloroplast ultrastructure. The maximum net photosynthetic rates (at 20°C) recorded for Larix leptolepis were higher than those for the evergreen conifers when expressed on a leaf weight basis but not when expressed per unit leaf area. The photosynthetic efficiency of new needles in the evergreen species showed an overall decline from just after needle maturity until just before budbreak in their second season, after which photosynthetic rates recovered temporarily, approaching previous maximum levels. There was no obvious correlation between seasonal photosynthetic efficiency (at 20°C) on the one hand, and daily air, and (30 cm) ground temperatures on the other, and there was no obvious winter suppression of evergreen photosynthetic rates. Evergreen needles showed starch loss and some membrane changes with the onset of winter, but there was no evidence for wintertime chloroplast clumping or membrane disruption.

The population biology of two species of eyefluke, Diplostomum gasterostei and Tylodelphys clavata, in perch

Abstract: Incidence, intensity and frequency distributions of infections in perch, Perca fluviatilis, with the eyeflukes Tylodelphys clavata and Diplostomum gasterostei were studied in a lake at monthly intervals over a period of two years. T. clavata had appeared in the lake immediately prior to the study, and its levels of infection continued to rise throughout the period of investigation whereas those of D. gasterostei remained relatively steady. The main period of infection of fish by both species of parasites was late summer, but a second and minor infection took place in spring. In the first year after its introduction T. clavata exhibited a seasonal cycle in incidence and intensity of infection and disappeared from fish in summer, but in the second year this cycle was masked by increased variation in development times and lack of synchrony throughout the parasite population. It is concluded that T. clavata has a life span of one year or less and that the parasites die within the fish, mainly in summer. D. gasterostei in contrast has a life span of at least one year, and disappearance of the parasite from the population is probably due to death of some heavily infected fish, although it was not possible to determine if this was due directly to the presence of the parasite.

Aquatic hyphomycete spora of some Dartmoor streams

Abstract: Changes in the aquatic hyphomycete spore content of three Dartmoor streams were followed throughout a 15-month period by Millipore nitration. Despite the fact that two of the rivers are not surrounded by deciduous trees, they contain a flora of aquatic hyphomycetes, including a number of distinctive forms which grow on Juncus and grass debris.

Mandeville and the Spirit of Capitalism

Abstract: Greed, avarice, rapacity, the quest for filthy lucre, are none of them traits peculiar to western Europeans of the last few hundred years — the capitalist epoch. Eastern potentates, feudal lords, magnates of the church, humble peasants, noble Romans, cultured Greeks and many others have been infected with the love of gold. The desire for wealth is not confined to capitalism; wealth for high living, conspicuous display or hoarding are all non-capitalist. Mediaeval and Renaissance monarchs shared with a number of ‘primitive’ tribes a taste for extravagant display. The hoarding of treasure typical of French peasants (at least until quite recently) is strikingly similar to the practices of wealthy Romans described by M. I. Finley. None of these people are capitalists in any strict sense of the word. Some of them own some means of production — although this would not necessarily be true of churchmen or princes who were the beneficiaries of systems forcibly expropriating a surplus from the producers. But even those who, like some peasants, own means of production, do not necessarily live in a capitalist system in a capitalist manner. They do not reinvest in order to procure further income; they merely exchange commodities for money, which is then exchanged for other commodities or hoarded (not ‘saved’ or invested, merely hoarded). Capitalism, on Marx's account, involves a different process — money is exchanged for commodities which are exchanged for money once more: M-C-M rather than C-M-C. In Capital Marx describes hoarding as a petrification of money; it exists in a naive form in traditional societies producing for a limited circle of wants.

The growth curve of the crustose lichen buellia canescens (dicks.) de not.

Abstract: SUMMARY Growth curves for Buellia canescens have been constructed using photographic measurements of thalli in situ over yearly intervals. The curves approximate to a simple model based on the assumption that relative growth rate is proportional to the area of thallus in an annulus of constant width within the growing margin.

The Upper Liassic Heteroptera of Mecklenburg and Saxony

Abstract: . Twenty-seven species of Heteroptera from the Upper Liassic of Dobbertin, Mecklenburg, and East Lower Saxony are redescribed and reclassified as follows. PROGONOCIMICIDAE (= Actinoscytinidae and Eocimicidae): Progonocimex jurassicus, P.liasinus (=Eocimex liasinus); Eocercopis ancyloptera, E.similis (=Cercoprisca similis); Archicercopis falcata. ARCHEGOCIMICIDAE (= Eonabidae and Diatillidea): Archegocimex geinitzi, A.primitiva (= Eonabis primitiva), A.liadis (=Archegocoris liadis); Somatocoris conservatus; Eurynotis incisus; Progonocoris pictus; Anosmus spilopterus; Entomecoris minor; Diatillus debilis; Corynecoris semigranulatus; Macropterocoris obtusus; Ensphingocoris praerotundatus. PACHYMERIDIIDAE (= Hypocimicidae, Sisyrocoridae and Psychrocoridae): Pachymeridium dubium; Sisyrocoris rudis; Hypocimex membranaceus; Apsicoria semideleta; Cathalus alutaceus; Psychrocoris cuneifera. CUNEOCORIDAE: Cuneocoris geinitzi. NAUCORIDAE (= Apopnidae and Aphlebocoridae): Apopnus magniclavus; Aphlebocoris punctata. Infraorder Gerromorpha incertae sedis: Engynabis tenuis. Progonocimicidae constitute the Infraorder Actinoscytinomorpha. Archegocimicidae, which have features recalling Pentatomomorpha, Cimicomorpha and Dipsocoromorpha, are left incerti infraordinis. Pachymeridiidae are probably Pentatomomorpha, and Cuneocoridae Dipsocoromorpha. The faunas therefore include representatives of four extant Infraorders, among them the earliest recorded Pentatomomorpha, Dipsocoromorpha and Gerromorpha.

Mass transfer by free convection during electrolysis at inclined electrodes

Abstract: The limiting electrolysis current technique has been used to obtain experimental measurements of mass transfer in natural convection at rectangular plane plates. Inclinations varying from horizontal down facing to horizontal upfacing at intervals of 10° have been employed with plate height and electrolyte concentration as additional variables. For attached boundary layer flow conditions, all results are well correlated by the equation: Attached flow conditions are obtained for all downfacing inclined orientations the vertical position and for upfacing inclinations where θ (the angle from the vertical) is small. Separation of the flow occurs at higher values of θ in upfacing orientations and is demonstrated by Schlieren photography, as is the existence of longitudinal vortices in the flow. The critical Rayleigh number for separation instability is estimated from the mass transfer measurements and compared with results of other authors. On a employe la methode basee sur un courant limiteur d'electrolyse pour obtenir des mesures experimentales d'un transfert de masse en convection qui impliquait des plaques rectangulaires et planes. On a utilise des inclinaisons vers le bas et vers le haut a des intervalles de 10°, la hauteur de la plaque et la concentration de l'electrolyte agissant comme des variables additionnelles. Dans le cas des conditions d'ecoulement dans la couche-limite, on a etabli une correlation satisfaisante entre les resultats obtenus et l'equation: On a obtenu des conditions d'ecoulement dans le cas de toutes les inclinaisons vers le bas, de la position verticale et des inclinaisons vers le haut dans lesquelles θ (l'angle avec la verticale) etait petit. La separation de l'ecoulement se produit pour des valeurs de θ plus elevees dans les inclinaisons vers le haut et on la demontre par une photographie de Schlieren de meme que l'existence de tourbillons longitudinaux dans le courant. On evalue le nombre critique de Rayleigh relatif a l'instabilite de la separation au moyen des mesures de transfert de masse et on le compare avec les resultats obtenus par d'autres auteurs.

The Statistical Analysis of Menstrual Bleeding Patterns

Abstract: A workshop was held in 1976 at the University of Exeter in England which concerned methods of statistically analyzing menstrual bleeding patterns. Such analysis relates to research concerning the new methods of contraception which affect menstrual and intermenstrual bleeding. The workshop participants experts in data collection and analysis in the field of menstrual blood loss agreed on the definition of terms. Data can be collected for such studies by daily records or by survey methods. It was agreed that the following types of information should be included in the data collection: 1) duration and amount of the bleeding periods; 2) variability of the bleeding-free interval; and 3) establishment of the bleeding pattern cycle. These indicators will facilitate comparison of data from the same woman over time or from different women at the same time.

New methods of detecting and studying saprophytic behaviour of aero-aquatic hyphomycetes from stagnant water

Abstract: Certain Hyphomycetes from stagnant water were found to colonize leaf material under the micro-aerophilic and anaerobic conditions of their natural habitat; this ability was greatly increased by higher oxygen tensions in a laboratory experiment. The fungi did not sporulate under conditions of oxygen depletion, but sporulation was induced by incubating in aerated water. Previous assay techniques may not have revealed the true distribution and abundance of this group. Species of Helicodendron, Helicoon and Aegerita were investigated.

Taxonomic studies on aquatic hyphomycetes

Abstract: This first paper in a series of taxonomic revisions of the genera of freshwater aquatic hyphomycetes describes general methods of isolation, culture and description. The six accepted species in Lemonniera de Wild. are illustrated. An extension of the generic concept is proposed, an artificial key to the species is included, L. pseudofloscula sp.nov. is described, and neo-types are provided for L. aquatica, L. cornuta and L. filiformis .

The distribution and function of microtubules in nutritive tubes.

Abstract: The density and distribution of microtubules in the nutritive tubes of three hemipteran insects, Corixa punctata, Notonecta glauca and Dysdercus cingulatus, were analysed from electron micrographs by computer. Both parameters varied amongst all three species, the density of microtubules in Corixa being approximately three times that seen in Dysdercus. The density and distribution of microtubules within the nutritive tubes correlated directly with the size of particle transported by them, suggesting that the microtubules may act as a sieve to preclude certain cellular components from entering the tubes. If microtubules are further involved in the generation of motive force for cytoplasmic transport along the nutritive tubes, this function is not dependent upon the number of microtubules, or upon their arrangement with respect either to each other or to the particle being transported.

Ovid's Metamorphoses G. Karl Galinsky: Ovid's Metamorphoses: An Introduction to the Basic Aspects. Pp. xi + 285; 1 plate. Oxford: Blackwell, 1975. Cloth, £6.

Abstract: Two important ideas run through this valuable work on the Metamorphoses. First, Ovid was primarily interested in myth as literature. Literary considerations must therefore take precedence over any other in evaluating and interpreting the poem. Secondly, 'Variety, both of subject-matter and tonality, is the keynote of the Metamorphoses' (p.l). Professor Galinsky uses these ideas energetically to discredit many popular and some scholarly misconceptions and half-truths about the genre, structure, style, and purpose of the poem. It is good to read that the Metamorphoses is about love rather than metamorphosis (p. 97), that its unity and coherence do not depend on a grand structural plan (ch. 2), and that uncritical use is too often made of labels like Augustan and anti-Augustan, epic and anti-epic, Virgilian and anti-Virgilian (pp. 11-12 and ch. 5). After clearing the ground for a new critical approach to the Metamorphoses Galinsky asks the right questions. How does the poem relate to Ovid's earlier work, to Hellenistic literature, and to the Aeneid? What is the function of metamorphosis in the poem? How does Ovid achieve his narrative effects? Galinsky's novel concepts of myth as literature and of variatio turn out to be critical tools with sharp cutting edges, enabling him to discuss these questions with insight, subtlety, and a wealth of detail. A comparison between Virgil's and Ovid's Aeneid demonstrates Ovid's variatio and individualistic use of myth and narrative techniques (pp. 217-51). Ovid's Aeneid, however, is hardly an altogether flattering example of the 'Ovidian alternative' to 'Vergil's achievement' and it seems unconvincing to argue in the context of this one episode that 'European literature would have been incalculably impoverished if Ovid had not provided a timely response and alternative to Vergil' (p. 248). The Metamorphoses as a whole, not this particular episode, is Ovid's counterpart to Virgil's epic. There are two reasons why Ovid's Aeneid is not entirely successful. First, Ovid was not capable of competing with Virgil on Virgil's ground. Even the successful parts of Ovid's Aeneid (Cyclops and Galatea; Circe; Glaucus and Scylla; the Sibyl) cannot be presented as a match for Virgil's achievement. Secondly, the blend of historical (Aeneas belongs to history) and non-historical elements which is found in the Metamorphoses after book 12 does not turn out well. Most readers will disagree with Galinsky when he says that i n Books 12-15 we find the same Ovid whom we encountered earlier' (p. 218). The atmosphere of the poem changes and we no longer feel the same kind of imaginative involvement in the stories (including that of Aeneas) that was felt up to book 12.

The ‘Hyporchema’ of Pratinas

Abstract: Et. d'un chant de P. (Snell: Trag. Gr. Frag. I, p.82) qui apparait comme un exemple de style dithyrambique pre-pindarique, qui comporte egalement des elements de parodie metrique.

Dimensions of the perception of art: verbal scales and similarity judgements.

Abstract: .— An INDSCAL analysis was performed on subjects' similarity judgements of all pairs of 12 landscape paintings. Three principal INDSCAL dimensions were identified by analysing responses to 24 unidimensional rating scales derived from previous experiments. The present findings, together with those of previously published studies, suggest that three of the principal dimensions of perception of art appear to be (1) Hedonic-Representational, (2) Clarity, (3) A Dynamic factor involving activity, balance and symmetry. It is suggested that although Complexity may be an important factor influencing responses to simple stimuli, its role in the perception of paintings is small, and has frequently been over-emphasised.

Lateglacial Raised Shorelines and Deglaciation in the Earn-Tay Area

Abstract: Analysis of altitude data obtained by accurate levelling at frequent intervals along raised shoreline and fluvioglacial terrace fragments permits the recognition of five Lateglacial raised shorelines sloping down towards E13°S at gradients that diminish with decreasing age and altitude from 0.51 to 0.24 m/km. There is evidence of several additional stages in the Lateglacial shoreline displacement on which the data are too sparse to permit the calculation of meaningful gradients. The lowest shoreline for which gradients were calculated descends eastwards beneath the carse deposits associated with the Main Postglacial Shoreline. The highest and most conspicuous feature, the Main Perth Shoreline, was formed whilst the decaying ice-sheet margin lay near Dunning and Perth, and Shorelines LP-1 to LP-4 were formed when the ice-margin lay not far from that position. The present elevation of the shorelines is explained in terms of an interplay between glacio-isostatic recovery, which was rapid during ice-wastage, and eustatic changes of sea-level. Consideration is given to the character of the raised beach sediments, and to the dissection of the raised estuarine flats.