Showing papers by "University of Exeter published in 1982"

Effect of collembolan grazing upon nitrogen and cation leaching from decomposing leaf litter

Abstract: Fragmented oak litter was incubated in the laboratory for 4 months with and without collembola. The effects of the animals upon fungal standing crop and leaching of inorganic nitrogen and cations was monitored over this period. The results showed that the fungal standing crop was higher in the presence of small numbers of animals than in litter lacking animals, yet at higher grazing intensities the fungal standing crop fell markedly. Significant increases in the leaching of ammonium, nitrate and calcium occurred as a consequence of animal grazing, but potassium and sodium losses from the litter were unaffected.

The Electrical Resistivity of Gold Films

Abstract: We present measurements of the d.c. electrical resistance of three classes of pure epitaxial gold films in the thickness range 30 to 900 nm. The combination of diverse morphological techniques with temperature-dependent data from 2 to 300 K enables us to apply a new theory based on those of Mayadas and Shatzkes for grain-boundary scattering, and of Soffer for surface scattering. Gold, evaporated and annealed on mica substrates, produced films which gave a mean microscopic surface roughness to Fermi wavelength ratio, r, of 0.05 and a grain-boundary reflexion coefficient, R$\_{\text{g}}$, of 0.45. On KBr substrates, samples, prepared similarly, formed two distinct type of film. Use of reflexion high energy electron diffraction and electron microscopy showed that the grain structure of these types of film differed; however, both gave an r of 0.1. An R$\_{\text{g}}$ of 0.10 was determined for one type but remained unknown for the other. Our results show how previous workers, often relying on the validity of Fuchs's theory and the misapplication thereof, have failed to present convincing evidence for specular surface scattering. We demonstrate the necessity for, experimentally, morphological observations and measurements over a wide temperature range, and, theoretically, the use of a method that combines the effects of both grain-boundary and angular-dependent surface scattering.

The accumulation of copper in Platichthys flesus L. and its effects on plasma electrolyte concentrations

Abstract: Copper was shown to accumulate in the gills, liver, kidney and plasma of sea water-adapted and freshwater-adapted Platichthys flesus exposed to elevated ambient concentrations of the metal. Exposure to sublethal concentrations of copper also caused deviations from control values, of the plasma ions sodium and chloride, indicative of impaired ion regulatory capacity.

Pressurization of cement in bones

Abstract: A seal member for fitting over and sealing the opening of a cavity in a bone to allow pressurization of cement in the cavity has an aperture for sealingly receiving a cement delivery nozzle. The seal member may be a balloon seal, which may be inflatable and expandable, or a solid body of conformable material. In use, the seal member is urged against the opening, e.g. by force applied by the barrel of a cement delivery gun on an abutment means having an apertured pressure piece shaped to urge the seal member against the mouth of the opening.

Alcohol and the Family

Abstract: In 1982 the present author wrote for WHO a paper entitled, “The Prevention and Management of Alcohol Problems in the Family Setting: A Review of Work Carried out in English-Speaking Countries.” This was subsequently published in Alcohol and Alcoholism in 1983 (Orford, 1983). The present chapter represents an update of that earlier paper with an extension to cover literature from other countries and literature written in languages other than English.

The effects of copper on ionic regulation by the gills of the seawater-adapted flounder (Platichthys flesus L.)

Abstract: Potentials measured in isolated, perfused gills fromPlatichthys suggest that the electrogenic ion-pump(s) contribute significantly to the potential measured in seawater. Copper added to the perfusate causes a significant reduction in the potential measured in the isolated gill and it is suggested that this is due to a direct inhibition of the branchial ion pump(s). Vascular resistance was unaffected by the presence of copper. Ouabain-sensitive oxygen consumption was reduced in tissue exposed to copper whereas residual oxygen consumption was unaffected, which suggests that the in vitro action of copper is confined to the Na+, K+ ATPase dependent portion of branchial metabolism.

The haptic perception of curvature.

Abstract: Ninety-two subjects, schoolchildren and undergraduate and postgraduate students, took part in a series of experiments on the haptic perception of curvature. A graded series of surfaces was produced using piano-convex lenses masked off to produce curved strips that could be explored without using arm movements. Thresholds were measured using the constant method and a staircase procedure. Experiments 1 and 2 yielded data on the absolute and difference thresholds for curvature. Experiment 3 demonstrated that the effective stimulus for curvature is represented by the overall gradient of a curved surface. Using this measure, it was shown that the present absolute thresholds for curvature are lower than those previously reported. In Experiment 4, absolute thresholds were compared using spherical and cylindrical curves: the results showed that, at least with the narrow strips used, the type of curvature does not exert a significant influence on performance. In Experiment 5, the subjective response to curvature was assessed using a rating procedure. Power functions are reported, although the relationship between stimuli and responses had a strong linear component. This suggests that haptically perceived curvature may be a metathetic rather than a prothetic continuum.

Time relationship between the respiratory cycle and limb cycle in the horse

Abstract: Summary Techniques developed for the detection and simultaneous recording of certain events in the respiratory and limb cycles are presented The respiratory cycle and limb cycle were found to be in-phase only at the canter and gallop The significance of any time relationship between events in respiration and in locomotion is discussed Resume On indique ici des techniques concues pour la recherche et l'enregistrement simultane de certains phenomenes de la locomotion et de la respiration Les cycles respiratoire et du mouvement des membres paraissent n‘etre “en phase” qu'au “canter” et au galop On discute la signification des relations existant ainsi entre la respiration et la locomotion Zusammenfassung Es werden Methoden beschrieben, die gewisse Ereignisse im Atemzyklus und Bewegungsablauf messen und simultan aufnehmen konnen Atemzyklus und Bewegungsablauf sind nur im langsamen (Canter) und schnellen Gallop aufeinander abgestimmt Die Signifikanz einer zeitlichen Beziehung zwischen Atmung und Fortbewegung wird diskutiert

The magnitude and frequency characteristics of fluvial transport in a devon drainage basin and some geomorphological implications

Abstract: Summary Magnitude and frequency analysis of fluvial transport based on long and detailed record has been lacking for British rivers. Continuous monitoring of suspended sediment and solute concentrations for the River Creedy, Devon since October 1972 has provided an opportunity to establish the medium-term magnitude and frequency characteristics of river transport in a sizeable (262 km 2 ) drainge basin. Results reveal the importance of solute removal, substantial variations in the relative magnitude of annual dissolved and suspended sediment yields, clear differences in the temporal distribution of sediment and solute removal, and contrasts in the magnitude and recurrence of extreme values of dissolved and suspended solids transport. Consideration of discharge levels most effective for transporting river loads in relation to a natural channel cross-section has stressed the importance of events of moderate magnitude and frequency in this drainage system.

Calpurnius Siculus and the Claudian Civil War

Abstract: In the first Eclogue of Calpurnius Siculus, Corydon and Ornytus seek to escape from the heat of the sun in a grove sacred to Faunus. There, on a beech tree, they find a long prophecy (lines 33–88), freshly carved by the god himself. After an introductory announcement of joyful news, the inscription proceeds as follows:Aurea secura cum pace renascitur aetaset redit ad terras tandem squalore situquealma Themis posito iuvenemque beata sequuntursaecula, maternis causam qui vicit Iulis.dum populos deus ipse reget, dabit impia victaspost tergum Bellona manus spoliataque telisin sua vesanos torquebit viscera morsuset, modo quae toto civilia distulit orbe,secum bella geret: nullos iam Roma Philipposdeflebit, nullos ducet captiva triumphos;omnia Tartareo subigentur carcere bellaimmergentque caput tenebris lucemque timebunt.

The nature of the clear zone around microtubules

Abstract: The clear zones seen around microtubules in transverse sections of nutritive tubes vary in size depending on whether a microtubule is bordered by ribosomes or by another microtubule. We consider that such a finding is not consistent with the current view, that the clear zone is maintained by microtubule-associated material. It can, however, be accounted for by an electrostatic repulsion between the surfaces of negatively charged microtubules and between microtubules and ribosomes which are also negatively charged. The experiments presented here, involving on the one hand the addition of cationic substances to microtubules and on the other the alteration in charge of the microtubules, support this hypothesis.

The Economic Effects of International Migration: A Survey

Abstract: The purpose of this paper is to present empirical evidence on the national economic effects of international migratory flows involving member countries of the European Communities (EC). Although these countries as a group constituted an area of net immigration in the post war period some member states have been important sources of emigration (Greece Italy Ireland) as have been the two applicant countries (Portugal Spain). The benefits and costs of this migration are examined for both sending and receiving countries and some conclusions are drawn in the final section. (EXCERPT)

Taxonomic studies on aquatic hyphomycetes: III. Some new species and a new combination

Abstract: Two new anamorph-genera of ‘aquatic hyphomycetes’ are erected: Tricladiopsis , to accommodate T. foliosa sp.nov. (type species) and T. flagelliformis sp.nov., and Sympodiocladium , with S. frondosum sp.nov. as sole representative. Other new anamorph species are: Articulospora atra, Flabellospora acuminata, Isthmotricladia britannica, Scorpiosporium rangiferinum, Sigmoidea aurantiaca, Sporidesmium ensiforme, Tricellula botryosa and Dwayaangam cornuta . Tetracrium amphibium is transferred to Flabellospora .

The effects of surface scattering upon resistivity

Abstract: It is shown how surface scattering may lead to substantial deviations from Matthiessen's rule. Using an angularly dependent surface scattering parameter as modelled by Soffer (1967), limit expressions for surface scattering in foils and wires are presented for both high and low kappa regions, where kappa is the ratio of the foil thickness, d, or wire radius, a, to the bulk electron mean free path, lambda infinity . From considerations for general values of kappa it is shown that surface scattering, at temperatures where the residual resistivity dominates, simply enhances the bulk temperature dependence. For higher temperatures for which the bulk resistivity varies as T5 the surface scattering can lead to an apparent T2 dependence. Further, it is shown that only for very thick samples or high temperatures where kappa >>1 is it possible to use a simplifying expression of the form rho - rho infinity =3/8 rho infinity lambda infinity /t, for the resistivity of foils or wires, where t is d or a. For most experiments the full theory is necessary to deduce rho infinity lambda infinity ; consequently virtually all previous determinations of this parameter are erroneous. Moreover, because of the influence of the surface scattering on the apparent temperature dependence of the resistivity, even of relatively thick material, several of the 'bulk' temperature dependences previously deduced for pure materials are almost certainly in error.

The effect of temperature on the survival of dry bryophytes

Abstract: Summary Loss of viability by seven species of bryophyte (Anomodon viticulosus, Racomitrium aquaticum, R. lanuginosum, Tortula intermedia, Andreaea rothii, Frullania tamarisci and Porella platyphylla) kept dry at temperatures between 20 and 100 °C was followed by estimating chlorophyll content after a moist recovery period. Behaviour at different temperatures was qualitatively similar, differing in time-scale. This ranged from a few minutes or less for 50% loss of chlorophyll at 100 °C to weeks or months for the more resistant species at 37 and 20 °C. For most of the species investigated, the logarithms of the half-viability times gave straight lines when plotted against the reciprocal of absolute temperature, with little variation of slope between species. The relation is similar to that shown by dry seeds and extrapolation suggests half-viability times of many years for the more desiccation-tolerant bryophytes at 0 °C or below. The two Racomitrium species showed curvilinear relationships, with notably great tolerance at temperatures in the middle part of the range investigated.

Nitrogen cycling in United Kingdom forests: the relevance of basic ecological research

Abstract: Following recent reviews on nutrient cycling in temperate and British forests, two aspects of N cycling are selected for examination because of their fundamental importance and their relevance to management-ecosystem research and mobilization of N during decomposition. Despite the early work by J. D. Ovington and P. J. Rennie, only two major forest ecosystem studies have been developed in Britain. Summaries from these ecosystems show that they span the range of temperate forests in the N cycling characteristics. The Pinus nigra plantation on Culbin Sands is functioning on a low capital with low rates of transfer and shows N deficiency after 40 years. In contrast, the mixed deciduous Meathop Wood has a much larger capital of N and higher rates of transfer. The Pinus ecosystem retained a high proportion of added fertilizer N in the biomass and forest floor, and increased growth rates can be explained through N recycling within the trees. Basic concepts of N mineralization are reviewed and it is shown that they need to be modified for application to forests. Uptake by saprophytic and mycorrhizal fungi from the pool of soluble organic N can short-circuit the ammonification pathway and N can be released from substrates with a high C:N ratio by lysis of microbial tissues and faunal feeding. Some examples of evidence of these processes are given, stressing the spatial and temporal mosaic of substrates acting as sinks and sources of N. Management practices can have a marked effect, not only on the quantity of N returned in residues, but on its availability as a result of variation in the associated carbon. However, growth experiments have shown that substrates with C:N ratios above 35 can release significant amounts of N to tree seedlings. A final examination of the recycling processes in the four nutritional stages of a forest emphasizes the importance of the effects of management on the short- and long-term balance of mobilization processes in the forest soil.

Three Hellenistic Personages: Amynander, Prusias II, Daphidas

Abstract: Amynander of Athamania first appears in our sources in 209 B.C. and last appears in 189 B.C. In whato follows I shall discuss two episodes from within this period.

A comparative study of the molecular motions in the three smectic phases of isobutyl 4(4′ phenylbenzylideneamino) cinnamate using incoherent neutron scattering

Abstract: Incoherent quasi-elastic neutron scattering results from aligned samples of isobutyl 4(4′ phenylbenzylideneamino) cinnamate in its smectic E, B and A phases are presented. The main results of a detailed analysis in conjunction with results from other techniques are as follows. Translational diffusion parallel to the layer normal is hindered in the SA phase by a weak temperature dependent barrier (5 to 15 kJ mol-1) but this is much stronger in the SB and SE phase (at least 30 kJ mol-1). However a feature of all three phases is that the molecules have the freedom to move diffusively on a time scale of 10-11 s by ∼ 1–4 A parallel to the layer normal. The molecules appear to undergo uniaxial rotational diffusion about their long axes in the SA and SB phases although it is not possible to discount some weak orientational ordering into six equivalent sites in the SB . In the SE phase there is a clear onset of orientational ordering into two sites separated by π. Dynamic fluctuation of the long molecular axes oc...

Production and reproduction of family farms in south-west england

Abstract: The paper examines the historical development of a sexual division of labour in the farm household in south-west England. The main focus is upon the transformation of women's work roles in the area studied from being primarily concerned with agriculture to being concentrated within the domestic domain. Women's contemporary domestic labour on the farm is of two sorts: on behalf of the family (reproductive labour) and for tourists (productive labour) accommodated within the house. The article traces the historical conditions under which this form of family farming arose. RESUME Cet article etudic l'evolution historique de la division sexuelle du travail dans les menages agricoles du Sud-Ouest de l'Angleterre. Il s'agit surtout de la transformation qui affecte les travaux accomplis par les femmes: au depart essentiellement tournes vers I'agriculture, ensuitc surtout vers le domaine domestique. Et ce travail domestique est actuellement a la fois un travail familial (de reproduction) et un travail (de production) pour les touristes accueillis dans la maison. l'article decrit les conditions historiques d'apparition de cc type d'agriculture familiale. KURZFASSUNG In dem Beitrag wird die historische Entwicklung einer geschlechtlichen Arbeitsteilung im landwirtschaftlichen Haushalt in Sudwestengland analysiert. Hauptaugenmerk wird der Umgestaltung der Rolle der Frauen im Arbeitsprozes im Untersuchungsgebied gewidmet, die ursprunglich in erster Linie auf die Landwirtschaft bezogen war und sich dann zunehmend auf den Haushalt konzentrierte Die derzeitige Arbeit der Frauen im landwirtschaftlichen Haushalt ist zweifacher Art. Fur die Familie (reproduktrve Arbeit) und fur Touristen (produktive Arbeit), die im Haus Untcrkunft haben. DerArtikel zeigt die histo-rischen Bedingungen auf, unter denen dicse Art der familienbetrieblichen Landwirtschaft entstanden ist.