Showing papers by "University of Leeds published in 1971"
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01 Jan 1971TL;DR: This paper shows that the gravity model is not a single model but that there is a whole family of spatial interaction models, and is particularly concerned with the disaggregation of such models, with the incorporation of time variables, and with the relation of spatial interactions to more general models.
Abstract: This paper shows that the gravity model is not a single model but that there is a whole family of spatial interaction models. The properties of this family are outlined in some detail. Basic concepts of such models can be developed in a variety of ways, and these are illustrated. The paper then outlines a number of other theoretical developments, and is particularly concerned with the disaggregation of such models, with the incorporation of time variables, and with the relation of spatial interaction, to more general, models. Uses of spatial interaction models are outlined briefly and the final section of the paper draws a number of conclusions and presents a summary.
474 citations
TL;DR: In this article, mathematical models of a motorcycle and rider dependent on three alternative assumptions concerning the tyre behaviour were developed. Stability characteristics deduced from them are compared, and m... and m...
Abstract: Mathematical models of a motorcycle and rider dependent on three alternative assumptions concerning the tyre behaviour are developed. Stability characteristics deduced from them are compared, and m...
381 citations
TL;DR: In this paper, a review of the yield behavior of polymers is presented, focusing on the importance of the hydrostatic component of stress, the viscoelastic nature of yield process, and the behaviour of oriented polymers.
Abstract: Recent research on the yield behaviour of polymers is reviewed. Particular attention is given to the importance of the hydrostatic component of stress, the viscoelastic nature of the yield process, and the behaviour of oriented polymers.
256 citations
TL;DR: In this article, a computer program based on a procedure discussed by Powell has been developed for the resolution of overlapping peaks in data output from x-ray diffraction, ion-exchange chromatography with spectroscopic detection, and infrared spectroscopy.
Abstract: A computer program based on a procedure discussed by Powell has been developed for the resolution of overlapping peaks in data output from x-ray diffraction, ion-exchange chromatography with spectroscopic detection, and infrared spectroscopy. A polynomial background is also fitted to the data so that recourse to arbitrary graphical methods for separating peaks and background is no longer necessary.
175 citations
171 citations
TL;DR: The ultrastructure of human bladder epithelium and bladder tumors has been examined with particular reference to the organization of well‐differentiated papillary carcinoma, with estimates of the potential growth rates obtained using the colcemid stathmokinetic technique.
Abstract: The ultrastructure of human bladder epithelium and bladder tumors has been examined with particular reference to the organization of well-differentiated papillary carcinoma. Estimates of the potential growth rates of the tumors have been obtained, using the colcemid stathmokinetic technique. The relation of cell organization to rates of division is discussed. Tumors of low malignancy have many of the ultrastructural features of normal epithelium; invasive tumors have a more simple cytoplasm with loss of specialization of the surface cells' unit membrane and suppression of telolysosome formation.
134 citations
01 Sep 1971
TL;DR: A survey of the most important aspect of arc-electrode processes (excluding externally heated cathodes) which concern engineers in a variety of applications is given in this paper, where the emphasis is on those characteristics which affect the design and operation of devices or processes in which they occur.
Abstract: The paper gives a survey of the most important aspect of arc-electrode processes (excluding externally heated cathodes) which concern engineers in a variety of applications. Although it is not possible to avoid discussion of the basic mechanisms and of the number of conflicting and still unresolved theories for them, the emphasis is, as far as possible, on those characteristics which affect the design and operation of devices or processes in which they occur. There is a brief general description of arc discharges and of important differences between them and glow discharges. After distinguishing between thermionic and nonthermionic cathodes (and commenting on the transitions of emission type which occur with some metals), the main body of the paper deals with nonthermionic cathodes. This begins with some of the chief observational data, such as current density, root splitting, electrode erosion, magnetic deflection, plasma jets and force on the cathode, and goes on to consider some of the important factors which affect cathode processes, including electrode material and surface state, current, gas and its pressure or vacuum. After commenting on zones within the cathode fall, there is a discussion of the many theories which have been put forward to explain the emission mechanism of cold-cathode arcs. It is suggested that no single process is responsible for all conditions, and that transitions in mode can occur, either abruptly or gradually, and the most significant principles and facts which must be taken into account are outlined. There is a short Section describing the main features of arc anodes, and the paper concludes with a discussion of electrode effects in mercury-arc convertors, gas-blast and oil circuit breakers, vacuum switches, arc heaters and plasma torches, arc welding, commutation and arc furnaces.
111 citations
TL;DR: Evidence is presented to substantiate the idea put forward in the barley paper that this decrease in the number of grains per unit area may be attributable more to a lower production of total dry matter by the high populations during the later stages of ear development, than to an unfavourable partitioning of such dry matter between the ear and the rest of the plant.
Abstract: Three wheat experiments are described in which a range of plant populations were shaded during different periods of development; in two of the experiments plant thinning was also carried out at a number of growth stages. Shading during the period of ear development caused an appreciable decrease in grain yield by decreasing the number of grains per ear. Shading during the grain filling period also reduced grain yield, this being brought about by decreased grain size. Thus in contrast to the barley experiments reported earlier (Willey & Holhday, 1971), these particular results gave no indication of a potential surplus of carbohydrate for grain filling and an associated limited ear capacity. However, when plant thinning was carried out at anthesis to make more carbohydrate available for grain filling in the remaining ears, grain yield per ear did not increase. It is argued, therefore, that grain yield probably was determined at least partly by a limited ear capacity. Plant thinning at earlier stages showed how the development of competition during the ear development period progressively reduced the potential capacity of the ear; the greater competition of higher plant populations accelerated this reduction in ear potential.From an examination of the effects of plant population, it is suggested that the number of grains per ear is the component having greatest influence on the decline in grain yield at above-optimum populations. The possible importance of the number of grains per unit area as an indicator of ear capacity on an area basis, and as a determinant of grain yield per unit area, is emphasized. A close relationship between grain yield per unit area and number of grains per unit area is illustrated for a number of plant-population response curves, and it is suggested that the decrease in grain yield at high populations is probably determined by a decrease in the number of grains per unit area. Evidence is presented to substantiate the idea put forward in the barley paper that this decrease in the number of grains per unit area may be attributable more to a lower production of total dry matter by the high populations during the later stages of ear development, than to an unfavourable partitioning of such dry matter between the ear and the rest of the plant.
107 citations
TL;DR: In this paper, a more accurate approximation for the power function of the likelihood ratio criterion for testing a simple null hypothesis against a class of composite alternative hypotheses is derived, and comparisons between the power functions of all three statistics are made.
Abstract: SUMMARY A more accurate approximation is derived for the power function of the likelihood ratio criterion for testing a simple null hypothesis against a class of composite alternative hypotheses. Two rival test statistics suggested by Rao (1965) and asymptotically equivalent to the likelihood ratio procedure are examined and approximations are obtained to their distributions under the null and alternative hypotheses. Comparisons between the power functions of all three statistics are made.
105 citations
TL;DR: This chapter systematically reviews the occurrence of parasitism and commensalism in Turbellaria throughout the class, with emphasis to modifications in structure, physiology, or life history, which appear to be related to the transition from the basic free-living habit.
Abstract: Publisher Summary Turbellaria are primarily free-living predators but each of their five orders contains families with representatives living in association with other animals. The commonest partners with which these associations are established include (1) echinoderms, (2) crustaceans, and (3) mollusks. One striking feature of these associations is the great extent to which Turbellaria show “host-type” specificity, in that the members of one family tend to be associated with a single type of host organism. Generally, commensalism implies the sharing of the same food by the turbellarian and its partner. This concept of commensalism provides a useful background against which most turbellarian associations can be considered. On the other hand, the parasitic turbellarians represent a climax to the gradual intensification of the relationship among commensal species and their particular partners and the other types of relationship noticed represent stages in the evolution of the parasitic habit. This chapter systematically reviews the occurrence of parasitism and commensalism in Turbellaria throughout the class, with emphasis to modifications in structure, physiology, or life history, which appear to be related to the transition from the basic free-living habit.
93 citations
TL;DR: In this paper, a general steady-state description is given of the critical conditions for explosion of an exothermic reactant mass of virtually unrestricted geometry in which heat flow is resisted both internally (conductive flow) and at the surface (Newtonian cooling).
Abstract: For an exothermic reaction to lead to explosion, critical criteria involving reactant geometry, reaction kinetics, heat transfer and temperature have to be satisfied. In favourable cases, the critical conditions may be summarized in a single parameter, Frank-Kamenetskii's $\delta $ being the best known, but analytical treatments are either confined to idealized geometries, namely, the sphere, infinite cylinder or infinite slab, or require the simplest representations of heat transfer. In the present paper a general steady-state description is given of the critical conditions for explosion of an exothermic reactant mass of virtually unrestricted geometry in which heat flow is resisted both internally (conductive flow) and at the surface (Newtonian cooling). The description is founded upon the behaviour of stationary-state systems under two extremes of Biot number-that corresponding to Semenov's case (Bi $\rightarrow $ 0) and that corresponding to Frank-Kamenetskii's case (Bi $\rightarrow $ $\infty $); it covers these and intermediate cases. For Semenov's conditions, the solution is already known, but a fresh interpretation is given in terms of a characteristic dimension-the mean radius R$\_{\text{S}}$. A variety of results for criticality is tabulated. For Frank-Kamenetskii's conditions, the central result is an approximate general solution for the stationary temperature distribution within any body having a centre. Critical conditions follow naturally. They have the simple form: $\left[\frac{q\sigma A\,\exp \,(-E/\boldsymbol{R}T\_{\text{a}})}{\kappa \boldsymbol{R}T\_{\text{a}}^{2}/E}R\_{0}^{2}\right]\_{\text{cr}}\equiv \delta \_{\text{cr}}$(R$\_{0}$) = 3F(j), where F(j) is close to unity, being a feeble function of shape through a universally defined shape parameter j, and $\delta \_{\text{cr}}$(R$\_{0}$) is Frank-Kamenetskii's $\delta $ evaluated in terms of a universally defined characteristic dimension R$\_{0}$-a harmonic square mean radius weighted in proportion to solid angle: $\frac{1}{R\_{0}^{2}}$ = $\frac{1}{4\pi}\mathop{\iint}\frac{\text{d}\omega}{a^{2}}$. Expressions for the mean radius R$\_{0}$ have been evaluated and are tabulated for a broad range of geometries. The critical values generated for $\delta $ are only about 1% in error for a great diversity of shapes. No adjustable parameters appear in the solution and there is no requirement of an ad hoc treatment of any particular geometric feature, all bodies being treated identically. Critical sizes are evaluated for many different shapes. For arbitrary shape and arbitrary Biot number (0 < Bi < $\infty $) an empirical criterion is proposed which predicts critical sizes for a great diversity of cases to within a few parts per cent. Rigorous, closely adjacent upper and lower bounds on critical sizes are derived and compared with our results and with previous investigations, and the status of previous approaches is assessed explicitly. For the most part they lack the generality, precision and ease of application of the present approach.
TL;DR: The most remarkable feature encountered is the presence of some unexplained bulbous inclusions distorting the tip of the haptonema but perhaps also present in a less extreme form in other types recently examined alive.
Abstract: Observations on the fine structure of two clones of zoids derived from Phaeocystis pouchetii s.l. are presented, with special reference to the scales, pyrenoids and haptonema, in which both clones agree. An unexplained difference between them in the form of a threadlike deposit external to the scales in one clone only is described in a preliminary way. The most remarkable feature encountered is the presence of some unexplained bulbous inclusions distorting the tip of the haptonema but perhaps also present in a less extreme form in other types recently examined alive. The interpretation of these findings is discussed.
TL;DR: In this article, the distribution and population dynamics of the meiofauna of a number of beaches on the Island of Sylt off the German North Sea coast were studied. But the authors focused on the meiobenthos of the beaches exposed to tides and wave action.
Abstract: Quantitative studies of the meiofauna of marine littoral sediments have been attempted only recently. Much of the work has been done in sheltered areas such as the Danish waddens (Muus, 1967), and in estuaries (Barnett, 1968; Capstick, 1959; Rees, 1940; Riemann, 1966), or in tideless areas such as the Baltic (Fenchel & Jansson, 1966; Fenchel, Jansson & von Thun, 1967; Jansson, 1968). Beaches exposed to tides and wave action have received less attention. Renaud-Debyser (1963) studied quantitative temporal variations in the meiofauna of beaches at the Bassin d'Arcachon, France, and Island of Bimini, Bahamas. Renaud-Debyser & Salvat (1963) have compared quantitatively the meio- and macrofauna of four beaches in the English Channel and six on the Atlantic coast of France. Schmidt (1968, 1969) has analysed quantitatively the distribution and population dynamics of the meiofauna of a number of beaches on the Island of Sylt off the German North Sea coast. Recently Mclntyre (1969) has reviewed the ecology of the meiobenthos. Subsequent to Mclntyre's review, in the U.S.A. quantitative investigations of the Gastrotricha (Hummon, unpublished) and Tardigrada (Pollock, 1970) of Massachusetts beaches have been made. Tropical beach meiofauna has been studied in India (Mclntyre, 1968), on the east coast of Malaya (Renaud-Mornant & Serene, 1967) and in Tuamotu, Polynesia (Salvat & Renaud-Mornant, 1969).
TL;DR: A steam-volatile extract, possessing a strong mushroom-like odour, has been isolated from Agaricus bisporus, the cultivated white mushroom of the mushroom grower as discussed by the authors.
Abstract: A steam-volatile extract, possessing a strong mushroom-like odour, has been isolated from Agaricus bisporus, the cultivated white mushroom of the mushroom grower. The major volatile components present, viz., 3-methylbutanal, 3-octanone, oct-1-en-3-one, 3-octanol, oct-1-en-3-ol, furfural, benzaldehyde, phenylacetaldehyde and benzyl alcohol, were identified by combined gas chromatography-mass spectrometry, and several other components were either positively or tentatively identified. The properties of the mushroom-like odour of oct-1-en-3-one and of the corresponding alcohol in dilute aqueous solution were examined.
TL;DR: Retention times for the trimethylsilyl ethers of more than fifty carbohydrates on 2% SE 52 columns and for the acetate derivatives of monosaccharides and polyols on 5% PEGA columns are given.
Abstract: Summary
Retention times for the trimethylsilyl ethers of more than fifty carbohydrates on 2% SE 52 columns and for the acetate derivatives of monosaccharides and polyols on 5% PEGA columns are given. The results of subsequent analyses of the soluble sugars and polyols in representatives of the following plant groups are described: algae (seven spp.), fungi (four spp.), lichen (ten spp.), bryophytes (six spp.), pteridophytes (five spp.) and angiosperm (seven spp.).
TL;DR: The separation of the components of the mixture is described using the technique of isoelectric focussing in polyacrylamide gel and it is found that the method was also found to be applicable to rat liver nuclei.
TL;DR: The Precambrian complexes of Galicia and Tras-os-Montes seem to be part of a plate of precambrian rocks thrust up from deep in the crust during the Hercynian orogeny onto Silurian sediments.
Abstract: The Precambrian complexes of Galicia and Tras-os-Montes seem to be part of a plate of Precambrian rocks thrust up from deep in the crust during the Hercynian orogeny onto Silurian sediments.
TL;DR: In this paper, the ignition delay of methanoloxygen and ethanol-oxygen mixed with 95 mole% argon was investigated and shown to parallel the behavior of methane and ethane, respectively.
TL;DR: If the three polypeptide chains of collagen had terminal segments with structures which facilitated rapid association and were then discarded, a puzzle might be solved and explain why biosynthesis of collagen takes minutes in vivo but much longer in vitro.
Abstract: If the three polypeptide chains of collagen had terminal segments with structures which facilitated rapid association and were then discarded, a puzzle might be solved. Such a mechanism could explain why biosynthesis of collagen takes minutes in vivo but much longer in vitro.
TL;DR: Further volcanic activity at Deception Island in the Antarctic has created a new strip of land across Telefon Bay, partly destroying the island formed by the 1967 eruption as discussed by the authors, which is known as Deception island deformation.
Abstract: Further volcanic activity at Deception Island in the Antarctic has created a new strip of land across Telefon Bay, partly destroying the island formed by the 1967 eruption.
TL;DR: An ultrastructural study of the earthworm body wall has revealed three types of sensory cells: multiciliate and uniciliate sensory cells, found only in the discrete sense organs and their cilia pass vertically through the cuticle, and scattered throughout the epidermis.
Abstract: An ultrastructural study of the earthworm body wall has revealed three types of sensory cells. Two, the multiciliate and uniciliate sensory cells, are found only in the discrete sense organs and their cilia pass vertically through the cuticle. The third type—isolated multiciliate sensory cells—are scattered throughout the epidermis and never grouped together. However, their cilia do not pass through the cuticle, but run horizontally over the outer surface of the epidermal cells. The structure of the sensory cells is described and compared with that of ordinary epidermal cells and the supporting cells found in the sense organs. Their possible physiological roles are discussed.
TL;DR: In this paper, holdfast samples of the kelp Laminaria hyperborea (Gunn.) Fosl, from fifteen approximately equidistant sites along the North-East coast of Britain, from St Abbs in Berwickshire to Flamborough Head, have been taken during the course of one spring-tide period.
Abstract: Seventy-two holdfast samples of the kelp Laminaria hyperborea (Gunn.) Fosl., from fifteen approximately equidistant sites along the North-East coast of Britain, from St Abbs in Berwickshire to Flamborough Head, have been taken during the course of one spring-tide period. The nematode fauna of these samples (20,744 specimens of 61 species) has been examined and the data are presented in such a way as to facilitate comparison with previous work. The fauna in the North Sea is dominated by large enoploid species. Enoplus communis Bastian, Anticoma acuminata (Eberth), Thoracostoma coronatum (Eberth), Phanoderma albidum Bastian and Pontonema vulgaris (Bastian) are regularly abundant. The minor contribution of the family Monohysteridae indicates that silt is of little importance to the nematode fauna in exposed localities. The holdfast-dwelling nematodes are generally epigrowth feeders or omnivores, the latter exploiting the sediment-feeding niche apparently unavailable to specialized deposit feeders. Species with short body setae, body length above 1·5 mm, having smooth cuticles and possessing some visual mechanism are dominant. It is upheld that algal structure per se is of primary importance in determining the different nematode communities found to exist in algae of different growth forms, and to account for the similarity shown between the faunas inhabiting similar algal growth forms from widely separate geographical areas and differing levels on the shore. It is suggested that habitat-component generic keys might facilitate investigation of unknown regions.
TL;DR: In this paper, a series of drawn non-crystalline poly(methyl methacrylate) samples are used to calculate orientation functions, which characterize the molecular orientation, and an excellent correlation exists between the measured birefringence and P 2 ( cos Δ) as expected from the aggregate theory.
01 Jan 1971
TL;DR: Although a number of possible applications of the Mossbauer effect have been suggested in the previous chapters, it is worthwhile to consider its use in general terms before developing the theme of more specific chemical application.
Abstract: Although a number of possible applications of the Mossbauer effect have been suggested in the previous chapters, it is worthwhile to consider its use in general terms before developing the theme of more specific chemical application. Generally speaking, three broad areas can be defined in addition to that of the basic phenomenon of resonant absorption itself; namely relativity and general physics, nuclear physics, and solid-state physics and chemistry.
TL;DR: There was a dose, positive relationship between milk intake and live-weight gain (LWG) before weaning, but weight gain after weaning was not significantly affected by the level of milk intake before weaned.
Abstract: Reconstituted milk substitute was given at two concentrations of powder (10% and 20%), each at four levels (10% powder—8, 12, 16 and 20% of live weight (LW); 20% powder—6, 8, 10 and 12% of LW) to 3 British Friesian male calves per treatment from 2 to 4 weeks after arrival, and the calves were weaned over the next 7 days. Chopped dried grass was offered to appetite before and for 3 weeks after weaning. The amount of solid food eaten was not affected by the dry-matter concentration of the milk substitute, but was significantly depressed as the amount of milk consumed increased. Between-treatment differences in solid food intake established at weaning persisted until the end of the experiment. There was a dose, positive relationship between milk intake and live-weight gain (LWG) before weaning, but weight gain after weaning was not significantly affected by the level of milk intake before weaning.
TL;DR: In this article, language and learning in the classroom are discussed and discussed in the context of the 1970s Language and Learning in the Classroom (LLLC) conference. Journal of Curriculum Studies: Vol. 3, No. 1, No 1, pp. 27-38.
Abstract: (1971). Language and Learning in the Classroom. Journal of Curriculum Studies: Vol. 3, No. 1, pp. 27-38.
TL;DR: It is suggested that under conditions of these experiments there was probably a potential surplus of carbohydrate available for grain filling and that grain yield was largely determined by the storage capacity of the ears, and the number of grains per ear as an indicator of individual ear capacity was emphasized.
Abstract: Two barley experiments are described in which a range of plant populations were shaded during different periods of development. Shading during the ear development period caused considerable reductions in grain yield, largely by reducing the number of grains per ear. Shading during the grain-filling period caused no reduction in grain yield. It is suggested that under conditions of these experiments there was probably a potential surplus of carbohydrate available for grain filling and that grain yield was largely determined by the storage capacity of the ears. The importance of the number of grains per ear as an indicator of individual ear capacity is emphasized.The effects of plant population on grain yield and its components are also examined. It is concluded that the number of grains per ear is the component having greatest influence on the decrease in grain yield at above-optimum populations and attention is again drawn to the possible importance of ear capacity. It is argued that on an area basis the number of grains per unit area may give a good indication of ear capacity. Examination of this parameter shows a close relationship with grain yield per unit area for both the shading and population treatments. It is particularly evident that a decrease in grain yield at high populations was associated with a comparable decrease in the number of grains per unit area. It is suggested that this decrease in grain number may be due to a lower production of total dry matter during ear development rather than an unfavourable partitioning of this dry matter between the ear and the rest of the plant. This lower production of total dry matter is attributed to the crop growth rates of the higher populations having reached their peak and then having declined before the end of the ear development period. This crop growth rate pattern, through its effect on grain number per unit area, is put forward as the basic reason why, in the final crop, grain yield per unit area decreases at above-optimum populations.