Showing papers by "University of East Anglia published in 1975"

A continuum theory of elastic material surfaces

Abstract: A mathematical framework is developed to study the mechanical behavior of material surfaces. The tensorial nature of surface stress is established using the force and moment balance laws. Bodies whose boundaries are material surfaces are discussed and the relation between surface and body stress examined. Elastic surfaces are defined and a linear theory with non-vanishing residual stress derived. The free-surface problem is posed within the linear theory and uniqueness of solution demonstrated. Predictions of the linear theory are noted and compared with the corresponding classical results. A note on frame-indifference and symmetry for material surfaces is appended.

Case Study and the Social Philosophy of Education Research

Abstract: (1975). Case‐study and the Social Philosophy of Educational Research. Cambridge Journal of Education: Vol. 5, No. 1, pp. 2-11.

Periphyton production and grazing by chironomids in Alderfen Broad, Norfolk

Abstract: Summary The standing crops of periphyton were measured on dead Typha stems and glass rods in a small, eutrophic lake from February to November. Chironomid larvae were also counted on the Typha stems; very few were present on the glass rods. The standing crop of periphyton on the Typha stems fell from 1.8 mg cm−2 in early April to nearly zero in November. On the glass rods the periphyton reached a peak of 1.93 mg cm−2 in late May and 1.94 mg cm−2 in July, thereafter falling to a steady level of 1.6 mg cm−2. The population of chironomids showed a peak in late May and then declined. The alimentary canals of chironomids collected fromTyphastems contained diatoms and filamentous algae so it appeared that chironomids were grazing down the periphyton. Chironomids moved on to theTyphastems in spring and returned to the mud in autumn. The periphyton is a richer source of essential amino acids than the mud, so that a movement from mud to reedstems in spring may increase the rates of growth and metamorphosis of the larvae. A crude production estimate gave a net primary production of periphyton of 170 mg dry wt m−2 day−1; the periphyton, however, would have contained bacteria and many small animals as well as algae.

A sex-chromosome hybrid zone in the grasshopper Podisma pedestris (Orthoptera : Acrididae)

Abstract: A sex-chromosome hybrid zone in the grasshopper Podisma pedestris (Orthoptera: Acrididae)

Climatic reversal in northern North Atlantic

Abstract: OVER the European arctic and subarctic seas the atmospheric circulation has recently tended towards northerly airflow, with an accompanying climatic deterioration. Since the 1950s direct northerly outbreaks have swept the Norwegian–Greenland Sea with increasing frequency, adding almost every year, particularly in the 1960s, to the severity of the climate in areas as far south as the British Isles. This change has been associated with the establishment over Greenland in the early 1950s of a persistent ridge of pressure anomaly and with its subsequent maintenance and intensification (on average) throughout the Jate 1950s and 1960s. Compared with the ‘normal’ climatic period of 1900–39 this cell represented an increase of over 3 mbar in the mean annual pressure at sea level in Greenland over the period 1956–65, but was very much more pronounced during the cold season (November–March). During the winter quarter (December–February), the increase in the mean pressure at sea level in Greenland amounted to over 7 mbar between 1900–39 and 1956–65 (Fig. 1a) and the pressure rise continued during the late 1960s. (Throughout, listed dates refer to the second year of the winter in question; thus, “winter 1956” refers to the period December 1955–February 1956.) A further increase of over 5 mbar occurred in Greenland between the winters of 1956–65 and 1966–70 (Fig. 1b). Coupled with a slight decrease of pressure over the eastern Norwegian and Barents Seas this change has resulted in “… a remarkable difference of pressure between Greenland and the eastern Norwegian Sea; this has increased since 1950 in every month of the year …”1.

Kinetic studies on the reaction between cytochrome c oxidase and ferrocytochrome c.

Abstract: In stopped-flow experiments in which oxidized cytochrome c oxidase was mixed with ferrocytochrome c in the presence of a range of oxygen concentrations and in the absence and presence of cyanide, a fast phase, reflecting a rapid approach to an equilibrium, was observed. Within this phase, one or two molecules of ferrocytochrome were oxidized per haem group of cytochrome a, depending on the concentration of ferrocytochrome c used. The reasons for this are discussed in terms of a mechanism in which all electrons enter through cytochrome a, which, in turn, is in rapid equilibrium with a second site, identified with 'visible' copper (830 nm-absorbing) Cud (Beinert et al., 1971). The value of the bimolecular rate constant for the reaction between cytochromes c2+ and a3+ was between 10(6) and 10(7) M(-1)-S(-1); some variability from preparation to preparation was observed. At high ferrocytochrome c concentrations, the initial reaction of cytochrome c2+ with cytochrome a3+ could be isolated from the reaction involving the 'visible' copper and the stoicheiometry was found to approach one molecule of cytochrome c2+ oxidized for each molecule of cytochrome a3+ reduced. At low ferrocytochrome c concentrations, however, both sites (i.e. cytochrome a and Cud) were reduced simultaneously and the stoicheiometry of the initial reaction was closer to two molecules of cytochrome c2+ oxidized per molecule of cytochrome a reduced. The bleaching of the 830 nm band lagged behind or was simultaneous with the formation of the 605 nm band and does not depend on the cytochrome c concentration, whereas the extinction at the steady-state does. The time-course of the return of the 830 nm-absorbing species is much faster than the bleaching of the 605 nm-absorbing component, and parallels that of the turnover phase of cytochrome c2+ oxidation. Additions of cyanide to the oxidase preparations had no effect on the observed stoicheiometry or kinetics of the reduction of cytochrome a and 'visible' copper, but inhibited electron transfer to the other two sites, cytochrome a3 and the undetectable copper, Cuu.

Convex polytopes with convex nets

Abstract: The idea of a net will be familiar to anyone who has made a model of a three-dimensional convex polytope (3-polytope) out of a flat sheet of card or similar material. To begin with, one cuts out a polygon, and then the model is formed by folding this and joining its edges in an appropriate manner. For example, Fig. 1 illustrates two nets for a regular tetrahedron. The folds are indicated by broken lines and lettering (either of the edges or of the vertices) indicates how the edges are to be joined.

Penny-shaped cracks

Abstract: The Somigliana formula is used to reduce an arbitrary elastic crack problem to a system of three integral equations for the components of displacement discontinuity. For the case of a penny shaped crack situated in an infinite isotropic medium with the crack faces subjected to arbitrary tractions, the integral equations are solved explicitly. In particular integral formulae are obtained for the stresses on the plane of the crack beyond the crack-tip, and hence for the stress intensity factors. The special case of uni-directional shear traction on the crack is examined.

Applications of an energy-momentum tensor in non-linear elastostatics

Abstract: For equilibrium states of elastic materials some general formulae of conservation type have been established in recent papers by Knowles and Sternberg and by Green. It is shown that these results arise naturally from the application of standard integral identities to an energy-momentum tensor first introduced into elastostatics by Eshelby. A duality is exhibited between the energy-momentum tensor and the Cauchy stress which leads directly to inverse deformation relations for elastic solids due originally to Shield.

Changes in the ecology of the Norfolk Broads

Abstract: Summary The Norfolk Broads have recently shown a marked loss of both floral and faunal diversity. To detect any recent changes and to provide a baseline for future research, twenty-eight broads were visited in 1972–73. Samples of aquatic flora and benthic fauna were taken and a number of physical parameters were measured. In the private broads a good inverse correlation between chlorophyll-a concentration and Secchi disc readings was found, suggesting that phytoplankton was largely responsible for the turbidity of the water. The relationship did not hold for the public broads where erosion and the stirring of sediments by motor launches is intense. Eleven broads were completely devoid of macrophytes. A macrophyte flora was well developed only in Upton and in the five Thurne broads and in these latter there was evidence of a recent loss in diversity. The sudden loss of formerly abundant species of macrophyte has been recorded frequently from the broads. The benthic fauna was poorly developed in most broads and was dominated by Limnodrilus hoffmeisteri and/or Potamothrix hammoniensis. Valvata piscinalis was the only regularly occurring gastropod in the benthos. Most of those broads with a diverse benthic fauna also had an abundant growth of macrophytes. Possible reasons for the recent changes in the ecology of the broads are discussed.

Numerical models of hydromagnetic dynamos

Abstract: The magnetic induction equation is solved numerically in a sphere for a variety of prescribed fluid flows. The models considered are the so-called ‘αω dynamos’, in which both small-scale turbulence and large-scale shearing play a significant role. Solutions are obtained by marching the finite–difference equations forward in time from some initial field. For a critical value of the magnetic Reynolds number Rm solutions which neither grow nor decay are found.Further calculations are performed with a ‘cut-off effect’ in which an attempt is made to simulate the effect of the Lorentz forces on the turbulence. For supercritical values of R, the magnetic field now stabilizes a t a finite value instead of increasing indefinitely. The form of the final field is compared with that produced at critical Rm in the absence of the cut-off effect.

Electron transfer between azurin and cytochrone c-551 from Pseudomonas aeruginosa.

Abstract: The electron-transfer reaction between azurin and cytochrome c1 isolated from Pseudomonas aeruginosa was investigated by rapid-reaction techniques. Temperture-jump studies clearly reveal two chemical relaxations, the amplitudes of which have ikentical spectral distributions, but relaxation times show different dependencies on reactant concentrations. Stopped experiments also showed complex kinetics. A model is proposed which is consistent with the kinetic and equilibrium data obtained. The central feature of this model is the proposal that two intercenvertible forms of reduced azurin exist in solution, only one of which si able to participate directly in the electron-transfer reaction with cytochrome c-551. Support for the hypothesis that two forms of reduced azurin exist is derived from studies on the electron-transfer reaction between azurin and Pseudomonas cytochrome oxidase. The possible physiological significance of such a situation is discussed.

A new method for the measurement of protein turnover.

Abstract: A new technique for the determination of rate constants of protein degradation is described. By using the method, half-lives of total soluble protein of Lemna minor during growth on full culture medium and distilled water were measured. The method involves incubating Lemna on a growth medium containing 3H2O. After a short exposure (20 min) to 3H-labelled culture medium, 3H was found in soluble amino acids, especially aspartate, glutamate, glutamine and alanine. After transfer to a 3H-free medium for 30 min, 80% of the 3H originally present in soluble amino acids was lost. These results suggest that 3H enters and leaves amino acids at the alpha-carbon atom, a conclusion supported by the observed labelling of glutamates. The exchange of H and 3H on the alpha-carbon atom is catalysed by transaminases and the speed of this exchange ensures that when the 3H2O is removed, the 3H in free amino acids is rapidly lost, thereby eliminating problems connected with metabolic pools and recycling. After an exposure of 20 min to 3H-labelled medium all protein amino acids, except for arginine, were found to be radioactive. The loss of radioactivity from protein amino acids was used to measure protein degradation.

Sexual reproduction in the monogenean Diclidophora merlangi: tissue penetration by sperms

Abstract: Copulation between pairs of adult Diclidophora merlangi detached from the host was frequently observed. The spined penis of one animal always attaches to a second worm at a latero-ventral position posterior to the genital openings. There is no vagina. The sperms travel between the cells of the recipient to reach the seminal receptacle. The ultrastructure of the sperm is described. Positions of adult D. merlangi on the gills of the host would facilitate pairing for sperm transfer.

The control of NAD specific malic enzyme from cauliflower bud mitochondria by metabolites.

Abstract: NAD malic enzyme (EC. 1.1.1.39) has been purified from cauliflower (Brassica oleracea. var. botrytis) bud mitochondria. The enzyme exhibits complex regulatory properties being activated by a variety of metabolites including glycolytic intermediates, CoA, sulphate and Krebs cycle acids—the tricarboxylic acids with the exception of citrate being more effective than dicarboxylic acids. Fructose diphosphate which is a positive effector of the enzyme increases the affinity of the enzyme for L-malate.

Applications of thallium(III) nitrate (TTN) to organic synthesis

Abstract: The scope and utility of thallium(III) nitrate (TTN) as an oxidant in organic synthesis is reviewed. Reactions which are described are the oxidations and oxidative rearrangements of olefins, acetylenes, ketones and compounds containing carbon-nitrogen double bonds. The effects of solvent on TTN oxidations are discussed, and the use of TTN/trimethyl orthoformate for the oxidative rearrangement of α,β-unsaturated carbonyl compounds is outlined. Preliminary investigations into TTN/support systems are described and their application to the oxidative rearrangement of alkyl aryl ketones is illustrated.

The steady streaming induced by a vibrating cylinder

Abstract: In this paper we apply the techniques of higher-order boundary-layer theory to study the steady streaming induced in the neighbourhood of a cylinder which vibrates harmonically, perpendicular to its generators, in an unbounded fluid. The theoretical predictions are compared with the results of experiments performed at high streaming Reynolds numbers. Improved agreement between theory and experiment is achieved although unresolved discrepancies remain.

The action of tributyltin on energy coupling in coupling-factor-deficient submitochondrial particles

Abstract: 1. Tributyltin at concentrations of approx. 1nmol/mg of protein induces respiratory control and lessens the protein permeability of coupling-factor-deficient submitochondrial particles. 2. At these concentrations or lower, it increases the P/O ratio of the particles to a small extent and inhibits the adenosine triphosphatase activity without greatly increasing its sensitivity to uncoupling agents. 3. It fails to stimulate ATP-driven reversed electron transport or transhydrogenase, but stimulates the transhydrogenase driven by aerobic succinate oxidation. 4. The results indicate that, unlike oligomycin, tributyltin does not discriminate between damaged and intact ATP-synthesizing complexes. 5. The relationship between the oligomycin- and tributyltin-binding sites is discussed.

The use of ratio-recording interferometry for the measurement of infrared emission spectra: Applications to oxide films on copper surfaces

Abstract: Infrared emission spectra from metal samples with oxide surface layers are shown to be very advantageously studied using the spectrum-ratioing facility of a recording infrared interferometer. The emission from a given sample is ratioed against that from a black-body emitter at the same temperature so as to give emittance as a function of wavenumber directly. This method has very useful application to irregularly shaped metal emitters. In the absence of selective reflection there is a direct correspondence between emission and absorption spectra for thin layers of an emitting substance. However, the presence of selective reflection leads to reduced emission and to considerable differences in the appearance of