Showing papers by "University of Leeds published in 1976"
01 Oct 1976
TL;DR: The influence of the ellipticity parameter and the dimensionless speed U, load W, and material G on minimum film thickness was investigated in this paper, where conditions corresponding to the use of solid materials of bronze, steel, and silicon nitride and lubricants of paraffinic and naphthenic mineral oils were considered.
Abstract: The influence of the ellipticity parameter and the dimensionless speed U, load W, and material G parameters on minimum film thickness was investigated. The ellipticity parameter k was varied from 1 (a ball-on-plate configuration) to 8 (a configuration approaching a line contact). The dimensionless speed parameter was varied over a range of nearly two orders of magnitude. And the dimensionless load parameter was varied over a range of one order of magnitude. Conditions corresponding to the use of solid materials of bronze, steel, and silicon nitride and lubricants of paraffinic and naphthenic mineral oils were considered in obtaining the exponent on the dimensionless material parameter.
764 citations
TL;DR: In this article, the authors obtained a relationship between speed, stride length and body size from observations of living animals and applied this to dinosaurs to achieve estimates of their speeds, which were rather low.
Abstract: THE faster an animal walks or runs the longer, in general, are its strides. Many dinosaur tracks have been found from which stride lengths can be measured1 .I have now obtained a relationship between speed, stride length and body size from observations of living animals and applied this to dinosaurs to achieve estimates of their speeds. The estimated speeds are rather low—between 1.0 and 3.6 m s−1.
504 citations
Abstract: The analysis of an isothermal elastohydrodynamic lubrication (EHL) point contact was evaluated numerically. This required the simultaneous solution of the elasticity and Reynolds equations. In the elasticity analysis the contact zone is divided into equal rectangular areas and it is assumed that a uniform pressure is applied over each element. In the numerical analysis of the Reynolds' equation a phi analysis where phi is equal to the pressure times the film thickness to the 3/2 power is used to help the relaxation process. The EHL point contact analysis is applicable for the entire range of elliptical parameters and is valid for any combination of rolling and sliding within the contact.
393 citations
TL;DR: In this paper, the authors present an analysis of accessibility by private transport using a Hansen type measure of accessibility, which is confined to car-owning households residing in inner London.
Abstract: This paper presents an analysis of accessibility by private transport, using a Hansen type measure of accessibility. The data base is the 1962 London Travel Survey. The study is confined to car-owning households residing in inner London. A comparison of the patterns of accessibility associated with four measures of areal attractiveness - total employment, retail employment, households and population - is presented. The sensitivity of relative accessibilities to marginal changes in parameter values is analysed. Two aspects of the effect of the zoning system on the measurement of accessibility are investigated: the effects of zonal configuration and zonal aggregation. First, the implications of increasing the size of central area zones is analysed. Second, a comparison of patterns of accessibility calculated at the zonal and district levels is undertaken.[/p]
326 citations
312 citations
01 Jul 1976
222 citations
218 citations
TL;DR: The ability of a particular porphyrin to dimerize appears to parallel that of the corresponding iron(III) complexes (ferrihaems), although it is thought that ferrihaem do not exhibit further aggregation under these conditions.
Abstract: An investigation of the behavior of protoporphyrin IX, deuteroporphyrin IX, haematoporphyrin IX and coproporphyrin III in aqueous solution revealed extensive and complex aggregation processes Protoporphyrin appears to be highly aggregated under all conditions studied At concentrations below 4 muM, aggregation of deutero-, haemato- and coproporphyrin is probably restricted to dimerization At approx 4muM each of these three porphyrins exhibits sharp changes in spectra consistent with a "micellization" process to form large aggregates of unknown size This critical concentration increases with increasing temperature and pH, but is not very sensitive to variation in ionic strength Temperature-jump kinetic studies on deuteroporphyrin also imply an initial dimerization process, the rate constants for which are comparable with those for various synthetic porphyrins, followed by a further extensive aggragation The ability of a particular porphyrin to dimerize appears to parallel that of the corresponding iron(III) complexes (ferrihaems), although it is thought that ferrihaems do not exhibit further aggregation under these conditions
212 citations
TL;DR: In this paper, the central ignition of premixed gases in closed spherical vessels is discussed and three new categories of solution are presented: the approximate computer solution (Case 1), the Dimensionless Universal Expression (Case 2), and the Complete Computer Solution (Case 3).
196 citations
183 citations
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TL;DR: Varieties of early modern English attitudes to English phonology morphology syntax the expanding vocabulary changes of meaning as discussed by the authors have been identified as a major obstacle in the adoption of morphological morphology syntax.
Abstract: Varieties of early modern English attitudes to English phonology morphology syntax the expanding vocabulary changes of meaning.
TL;DR: In this paper, field, petrographic and geochemical criteria identify the Eocambrian, 500 km 2, mafic-ultramafic complex of Jabal al Wask as an ophiolite possibly formed in a back arc environment.
TL;DR: The drawing behavior of a series of linear polyethylene homopolymers with weight-average molecular weight (Mw) ranging from 67,800 to ∼3,500,000 and variable distribution was studied in this article.
Abstract: The drawing behavior of a series of linear polyethylene homopolymers with weight-average molecular weight (Mw) ranging from 67,800 to ∼3,500,000 and variable distribution (Mw/Mn = 5.1−20.9) has been studied. Sheets were prepared by two distinct routes: either by quenching the molten polymer into cold water or by slow cooling below the crystallization temperature (∼120°C) followed by quenching into cold water.
When the samples (2 cm long) were drawn in air at 75°C using a crosshead speed of 10 cm/min it was found that for low Mw polymers the initial thermal treatment has a dramatic effect on the rate at which the local deformation proceeds in the necked region. At high Mw such effects are negligible. An important result was that comparatively high draw ratios (λ > 17) and correspondingly high Young's moduli could be obtained for a polymer with Mw as high as 312,000. It is shown how some of the structural features of the initial materials (mainly studied by optical microscopy, small-angle x-ray scattering and low-frequency laser Raman spectroscopy) can be interpreted in terms of the molecular weight and molecular weight distribution of the polymers. Although crystallization and morphology can be important at low Mw, it suggested that the concept of a molecular network which embraces both crystalline and noncrystalline material is more helpful in understanding the drawing behavior over the whole range of molecular weights.
TL;DR: A compilation of all published and unpublished gravity data for the Eastern rift between latitudes 1°N and 5°S is presented in this paper, where the shape of the negative regional anomaly associated with the rift is approximately two-dimensional, striking east of north, of width 350 ± 50 km and amplitude500 ± 100 g.u.
TL;DR: Band 3 proteins rotate in the human erythrocyte membrane; rotation is almost certainly confined to an axis normal to the plane of the membrane and is characterised by a diffusion coefficient of the order of 1,000 s−1.
Abstract: Band 3 proteins rotate in the human erythrocyte membrane; rotation is almost certainly confined to an axis normal to the plane of the membrane and is characterised by a diffusion coefficient of the order of 1,000 s−1. Spectrin does not restrict rotational motion of band 3 proteins.
TL;DR: Tamoxifen inhibited the binding of [3H]oestradiol to 8S oestrogen-binding components, derived from rat uteri and DMBA-induced tumours, in vitro and the determination of specific oestrogens- binding components in vitro was significantly reduced.
Abstract: Tamoxifen (ICI 46,474) has been shown to possess anti-tumour properties in the dimethylbenz(a)anthracene (DMBA)-induced rat mammary carcinoma model During tamoxifen therapy the binding of [3H]oestradiol in vivo to uterine (P less than 0-001), vaginal (P less than 0 X 01) and tumour (P less than 0-001) tissues was significantly reduced Tamoxifen therapy was without effect on the binding of [3H]oestradiol in heart tissue The determination of specific oestrogen-binding components in vitro was significantly reduced (P less than 0-01) in tumours from tamoxifen-treated rats and tamoxifen inhibited the binding of [3H]oestradiol to 8S oestrogen-binding components, derived from rat uteri and DMBA-induced tumours, in vitro
TL;DR: The extent to which a set of related graph-theoretic properties can be used to accont for the superlinear complexity of computational problems is explored and certain limited lower bounds can be proved by means of such properties.
TL;DR: In this paper, the growth of nitride on spec-trographically pure Si was investigated in the range 1250° to 1370°C for N2 pressures of 20 to 760 torr.
Abstract: The kinetics and morphology of the growth of nitride on spec-trographically pure Si were investigated in the range 1250° to 1370°C for N2 pressures of 20 to 760 torr. A model is presented which explains all the observations. The initial linear kinetics are associated with the growth of individual nitride nuclei. As the nuclei coalesce, the reaction rate steadily decreases, finally falling effectively to zero when the Si is completely covered with nitride. The model indicates how the microstructure of reaction-sintered Si3N4 may be controlled.
TL;DR: In this paper, a model for the strain during the growth and propagation of shear zones is proposed for the deformation of mafic and felsic minerals within a ductile shear zone of short finite length from Botswana and a much longer planar hear zone from North Uist, Scotland.
TL;DR: The theory of water uptake by a single root is reviewed in this article, including infinite and finite systems, and constant and variable diffusivity, and it is likely that local rates may, on occasion, be much larger than the averages, and the possibility of large gradients cannot be dismissed.
Abstract: The theory of water uptake by a single root is reviewed, including infinite and finite systems, and constant and variable diffusivity. This theory predicts the water potential and content at the root surface will depend upon soil and root parameters, most of which are readily determinable, but the uptake rate of water per unit length of root is uncertain. Uptake rates averaged over whole root systems will usually be small, suggesting only very small gradients of water content around roots, but it is likely that local rates may, on occasion, be much larger than the averages, and the possibility of large gradients cannot then be dismissed. Certain special effects may alter these conclusions, particularly salt accumulation around roots and no contact or partial contact of roots with soil. Both demand a fast uptake rate of water before they become important, and salt accumulation is unlikely to be important except in saline soils. Methods of dealing with whole root systems are briefly considered. Differing root density can be dealt with by subdividing the root volume into compartments, or by regarding the problem as one of dispersion pattern. Further advance requires better information about local boundary conditions imposed by roots on the surrounding soil.
TL;DR: In this paper, the authors interpreted the structure of gas-nitrided dilute Fe-Ti alloys in terms of a periodic array of equiatomic Ti-N mono-layer plates on the cube planes of the matrix.
TL;DR: In this article, the second order Legendre polynomial was used to derive the expected relationship between the orientation and the degree of crystallinity of poly(ethylene terephthalate) tapes.
TL;DR: In this paper, some of the elementary ideas underlying catastrophe theory are reviewed and it is shown how the cusp catastrophe can be used in the theory of binary choice, a specific application to modal choice is presented and a number of conjectures are made about the wider application of the method in urban modelling.
Abstract: Some of the elementary ideas underlying catastrophe theory are reviewed and it is shown how the cusp catastrophe can be used in the theory of binary choice. A specific application to modal choice is presented and a number of conjectures are made about the wider application of the method in urban modelling.
TL;DR: In this article, the Variscan arc in the Iberian Peninsula is classified as a primary or secondary curvature. But the curvature of the arc is not defined.
Abstract: Many mountain ranges (Alps, Carpathians, Himalayas) and volcanic island ridges (Aleutians, Banda, Mariana) are curved or sinuous, often so regularly as to be described as arcs. Their curvature may be primary or secondary. Among numerous models proposed to account for the curvature are the orocline or secondary bending hypothesis of Carey (1958), the inextensional bending model of Frank (1968) and the spreading of marginal seas and lateral compression (Matsuda & Uyeda 1971). Different models imply different patterns of finite strain. Palaeomagnetic measurements can also be used to discriminate between them. Criteria for discriminating are examined, with particular reference to the Variscan arc in the Iberian Peninsula.
TL;DR: The administration of glucose, but not of fructose or sucrose, to starved rats alters the response to heparin injection towards that found in rats in the fed state, and the effect of changes in nutritional status on the activity of clearing factor lipase in rat post-heparin plasma depends on theHeparin dosage used.
Abstract: 1. In rats in a variety of nutritional states, the adipose tissue clearing factor lipase activity is strongly, positively correlated with fat-cell triglyceride fatty acid uptake. 2. In the same animals, muscle clearing factor lipase activity is inversely correlated with the activity of the enzyme in adipose tissue and with the plasma insulin concentration. 3. In starved animals that are given glucose, adipose tissue clearing factor lipase activity is positively correlated with the plasma insulin concentration. 4. The effect of changes in nutritional status on the activity of clearing factor lipase in rat post-heparin plasma depends on the heparin dosage used. The administration of glucose, but not of fructose or sucrose, to starved rats alters the response to heparin injection towards that found in rats in the fed state.
TL;DR: In this paper, the deformation behavior at low plastic strains of three Al-MgSi alloys in the fully aged condition has been studied, and it is concluded that intergranular failure in BD6 and BD8 is suppressed at low strains because the associated stress concentrations are insufficient to produce decohesion at the grain boundary precipitates.
TL;DR: In this paper, a critical account of the recent investigation on the chemical modification of lignocellulosic sisal fibers is presented, where the molecular structure of the paracrystalline cellulose, which forms the major constituent of the fiber, was studied by x-ray diffraction technique.
Abstract: A critical account has been presented of the recent investigation on the chemical modification of lignocellulosic sisal fibers. The molecular structure of the paracrystalline cellulose, which forms the major constituent of the fiber, was studied by x-ray diffraction technique. Scanning electron microscope examination of the multicellular structure, surface topology, and fracture morphology of the fiber was carried out. The mechanical properties of the sisal ultimate cell and the “technical” fiber have been investigated by means of a microextensometer and an Instron tensile tester, respectively.