Showing papers by "University of Manchester published in 1973"

Garnet-orthopyroxene and orthopyroxene-clinopyroxene relationships in simple and complex systems

Abstract: Use of simple mixing models of orthopyroxene and garnet solid solutions enables extrapolation of experimentally determined equilibria in the MgSiO3-Al2O3 system to uninvestigated parts of pressure-temperature-composition space. Apparent discrepancies in the experimental data for simple and multicomponent systems may be explained by considering the effect of CaO and FeO on reducing pyrope activity in the garnet solid solutions. Equilibration pressures of natural garnet-orthopyroxene assemblages may be calculated, provided temperatures are known, from a combination of the experimental data on the MgSiO3-Al2O3 system and analyses of coexisting natural phases. Despite the presence of a compositional gap in the system, the solubility of enstatite in diopside coexisting with orthopyroxene can also be approximately treated by an ideal solution model. An empirical approach has been developed to take account of Fe2+ on the orthopyroxene-clinopyroxene miscibility gap in natural systems in order to calculate equilibration temperatures of 2-pyroxene assemblages. The model presented reproduces almost all of the available experimental data for multicomponent systems to within 60° C.

Transient analysis of underground power-transmission systems. System-model and wave-propagation characteristics

Abstract: A mathematical model suitable for the analysis of travelling-wave phenomena in underground power-transmission systems is presented. The model is developed in terms of a generalised angular frequency, and may therefore be applied to the solution of steady-state problems or, by means of Fourier-transform techniques, to the solution of transient problems. The model takes into account skin effect in the conductors and in the soil. It is then shown how the system model may be analysed using multiconductor-transmission-line theory to give the transient response of the cable system. The wave-propagation characteristics are given for the natural modes of a certain cable system. These characteristics are examined with a view to their implications on transient phenomena.

A “Level–Shifting” method for converging closed shell Hartree–Fock wave functions

Abstract: A discussion of Hartree damping in closed-shell Hartree-Fock theory is given indicating when the method might force convergence of intrinsically divergent cases. An alternative, but closely related principle, “level shifting” is described, and the advantages of the latter procedure discussed.

The Granulite Facies, Partial Melting and the Archaean Crust

Abstract: As chairman of a session of the meeting I would like to add a few comments concerning some of the problems discussed. During the discussions certain important conclusions have appeared. The detailed descriptions presented of the oldest known samples of the Earth indicate that at that time the crust had already a remarkably similar structure and chemistry to that of more modern times. It has also been made clear that rocks of the granulite facies make a massive contribution to the base of the ancient crust and logically could make a large contribution to modern regions under batholith zones of mobile belts, where the crust has been thickened by tectonic events. It also seems possible that the mantle processes controlling tectonics in the Archaean, while having some features in common with the present regime, were unique. Most models of the Earth's thermal history (Birch i965) suggest a very hot initial stage and it is difficult to see how the general geochemical equilibrium state of the Earth could be achieved without a very large degree of melting at some period of Earth history. If a large molten fraction is assumed, it would be difficult to preclude very complex convective structures. Crust will appear when surface temperatures approach 800 ?C whichl could be at a very early stage indeed. When liquid water appears on the surface at 100 ?C or less, a crust a few kilometres thick would rapidly form. Some present models (Finale I97I) indicate that formation of a hydrosphere might be an early event and this process itself would accelerate initial cooling. It might well be expected that the earliest semi-stable crustal fragments would be granitic. Such materials would be capable of floating on basalt liquids while solid basalt would be rapidly engulfed. This crust would also concentrate radioactive species (see Heier, this volume). When an aqueous phase is present, weathering would be intense partly on account of the supply of acids from intense volcanism ancd also from the supply of glassy volcanic debris. Early geochemical separation processes associated with a hydrosphere would thus be intense and synchronous with thicker crust formation. The initially radioactive crust could well have been associated with thermal gradients of the order of 100 ?C km-' and could hardly be thicker than 10 km before belting would occur at the base with the occurrence of igneous overturn of the material. It is now also abundantly clear that the appearance of simple life forms and the hydrosphere 'were separated by a very brief period so that bio-geochemical precipitates and bio-geochemical separations might also operate on the primitive surface at a very early stage.

Design of dynamical and control systems by the method of inequalities

Abstract: In the design of dynamical systems, such as automatic regulators and electrical networks, a system is required to satisfy constraints and specifications, which can be represented by a set of simultaneous algebraic inequalities. It is shown how typical design problems lead naturally to the formulation of a set of inequalities, any solution of which characterises an acceptable system. A numerical process for obtaining a solution of a system of inequalities is developed. Applications of the method of inequalities to the design of automatic control systems are discussed. Specific control problems, in single-variable and multivariable systems, are considered, and designs, obtained by the method of inequalities, are compared with those obtained by standard methods of Nyquist, root locus and optimisation.

The elasticity and related properties of rubbers

Abstract: The relation of rubbers to other classes of polymers and the molecular basis of rubber elasticity are briefly examined. The methods used in the quantitative development of the statistical-thermodynamic theory of a molecular network are outlined, and the main conclusions, in the form of stress-strain relations, etc, are presented and compared with experimental data. Also examines the photoelastic properties of rubbers from both theoretical and experimental standpoints and discusses in detail the evidence derived from photoelastic studies on the statistical segment length in the molecular chain and its relation to intramolecular energy barriers. The thermodynamic analysis of stress-temperature data for rubber and other polymers, with particular reference to the internal energy and entropy changes during extension under constant pressure or constant volume conditions is studied. The phenomena of swelling in liquids is considered.

Some thoughts on agentivity

Abstract: The term ‘agentive’ is a familiar one in current discussions of the syntax of English (and other languages). Although most who use it seem, at first glance, to be referring to more or less the same semantic feature, the term is employed in a variety of ways. For instance, Fillmore (1968: 24) talks of an ‘agentive case’; Gruber (1967: 943) has ‘agentive verbs’; Lyons and others speak of ‘agentive nouns’; while Halliday (1967: 196), although he does not use the term ‘agentive’, distinguishes a feature of clauses which is clearly related to the notion of agentivity. Apart from this disagreement as to what, precisely, the term ‘agentive’ is to be predicated of, there is a further divergence of opinion over which nouns (or verbs, etc.) are to be considered agentive. For instance, Lyons marks the surface subject of see as agentive (1968: 387). Fillmore, on the other hand, assigns this to the dative case, and Gruber classifies see as a non-agentive verb. Again, Lyons and Halliday take up what are in effect incompatible positions with regard to the status of the prisoners in John marched the prisoners. In view of this indeterminacy, it seems worthwhile to attempt a critical examination of the notion of agentivity, in the hope that a clearer characterization of it might emerge.

On the exterior problems of acoustics

Abstract: The method of integral equations is the most familiar method of proving existence theorems for the Helmholtz equation of acoustics. The wave potentials are expressed as surface distributions of wave sources (for the Neumann problem) or wave dipoles (for the Dirichlet problem). By a wave source is meant the free-space wave source. The source and dipole strengths for the exterior potentials are found to be solutions of Fredholm integral equations of the second kind which are, however, singular at a certain discrete set of frequencies corresponding to eigensolutions of the interior problems. The existence of exterior solutions at the expected frequencies can still be shown, but the proof involves a detailed and complicated study of the interior solutions. It is physically evident that this difficulty arises from the method of solution and not from the nature of the problem.

Regional and historical aspects of lead pollution in Britain.

Abstract: Two major periods of increase in atmospheric lead concentrations have been recognized in the Northern Hemisphere—the first resulting from the rapid growth of industry during the eighteenth and nineteenth centuries, the second from the great expansion of motor vehicle traffic since the end of the Second World War1,2. There is clear evidence of lead pollution caused by motor vehicles close to busy roads2–4, and the three-fold increase in lead concentrations in snow from the Greenland ice-cap during the past 20 yr has also been correlated with the emission of lead aerosols from car exhausts1. In Britain many minerals, including lead, have been exploited over a long period of time, but some, including lead, have declined in importance in the past 100 yr after peak extraction levels in the eighteenth and nineteenth centuries. Thus it is probable that in certain areas of Britain heavy metal pollution has been worse in the past than it is now. This communication examines the historical trends in lead pollution in Britain by use of nineteenth century and present-day moss specimens, and by peat profiles—methods used also by other workers to demonstrate historical trends in heavy metal pollution in Scandinavia2,5.

The absorption of protons with specific amino acids and carbohydrates by yeast

Abstract: 1. Proton uptake in the presence of various amino acids was studied in washed yeast suspensions containing deoxyglucose and antimycin to inhibit energy metabolism. A series of mutant strains of Saccharomyces cerevisiae with defective amino acid permeases was used. The fast absorption of glycine, l-citrulline and l-methionine through the general amino acid permease was associated with the uptake of about 2 extra equivalents of protons per mol of amino acid absorbed, whereas the slower absorption of l-methionine, l-proline and, possibly, l-arginine through their specific permeases was associated with about 1 proton equivalent. l-Canavanine and l-lysine were also absorbed with 1–2 equivalents of protons. 2. A strain of Saccharomyces carlsbergensis behaved similarly with these amino acids. 3. Preparations of the latter yeast grown with maltose subsequently absorbed it with 2–3 equivalents of protons. The accelerated rate of proton uptake increased up to a maximum value with the maltose concentration (Km=1.6mm). The uptake of protons was also faster in the presence of α-methylglucoside and sucrose, but not in the presence of glucose, galactose or 2-deoxyglucose. All of these compounds except the last could cause acid formation. The uptake of protons induced by maltose, α-methylglucoside and sucrose was not observed when the yeast was grown with glucose, although acid was then formed both from sucrose and glucose. 4. A strain of Saccharomyces fragilis that both fermented and formed acid from lactose absorbed extra protons in the presence of lactose. 5. The observations show that protons were co-substrates in the systems transporting the amino acids and certain of the carbohydrates.

The weak friction approximation and tidal evolution in close binary systems

Abstract: The aim of this paper is to study the dynamical problem of tidal friction in a binary system consisting of deformable components, with the restriction that the angle of lag or advance of the tidal distortion with respect to the direction of the disturbing companion is small. The fractional distortion of the bodies due to rotation and tidal interaction is also treated as a first-order small quantity, and terms up to the fourth harmonic in the tidal potential are retained. In this linear approximation, the time-dependent tidal potential can be Fourier decomposed into a spectrum of simple harmonic terms, each of which is responsible for raising a ‘partial wave’ in the body; each such partial wave can then be treated independently of the others. This is the method first employed by Darwin. In Section 2, it is assumed that the phase lag in the response of the body (due to dissipation of kinetic energy of deformation) is proportional to the forcing frequency, which is justified for small amplitude oscillations of a viscous fluid or visco-elastic body. A simple expression is then obtained for the potential function for the distortion in terms of the disturbing potential and the structure of the body. In Section 3, the distortion potential function is employed in deriving the componentsR, S andW of the disturbing force which are then substituted in the Gaussian form of the equations for variation of the elements. In Section 4, the Eulerian equations for motion of deformable bodies are derived, using the so-called ‘mean axes’ of the body as the rotating axes of reference. In Section 5, it is shown that the dynamical effects of rotational distortion occur on a much shorter time scale than those arising from tidal friction, which allows one to consider the two phenomena as acting independently of one another. The collected set of Gaussian (orbital) and Eulerian (body) equations is re-written in terms of dimensionless variables for the tidal friction case, and the stability of the system is examined on the basis of these equations. In Section 6, the tidal friction equations are integrated numerically for the close binary system AG Persei and for the Earth-Moon system. In the former, the integrations were started from a highly elliptical orbit and the system was found to relax into a circular orbit, with synchronous rotation perpendicular to the orbit. In the latter, the integrations were performed backwards in time from the present day, and it was found that the lunar orbit rapidly becomes highly elliptical at the time of closest approach, thus indicating a probable capture of the Moon by the Earth. This result is in agreement with that obtained by other investigators; however, it is shown that the detailed behaviour of the system at the time of capture, in particular the inclination of the lunar orbit to the ecliptic, depends critically on the chosen rate of dissipation in the Moon's interior. A simple argument is presented which allows an estimation for the mean viscosity of a fluid body from the known age of the system: for the components of AG per, the result is 2×1011 g cm−1 s−1, indicating that the stars must have possessed turbulent convective outer regions during some part of their tidal evolution, while for the Earth, the result, is 1.4×1012 g cm−1 s−1. It is shown that the angle of tidal lag in nonsynchronous close binary systems in general is expected to be extremely small, and not observationally detectable.

Vulnerability of Developing Brain: Relative Effects of Growth Restriction during the Fetal and Suckling Periods on Behavior and Brain Composition of Adult Rats

Abstract: Growth restriction was achieved by underfeeding mother rats during pregnancy and lactation. Offspring were either ( i ) adequately nourished during the fetal and suckling periods, (ii) undernourished during both, or (iii) and (iv) undernourished during one or the other period. All rats were fed ad libitum from weaning. The post- natally underfed animals were the most efficient at running a maze for a food reward. Differences in levels of motivation were sought using a Skinner box in which rats learned to press a lever for food. Normal rats had the lowest lever-pressing rate and those re stricted both pre- and postnatally had the highest. The tendency to inhibit movement to avoid an electric shock was weakest in normal rats and greatest in the doubly deprived animals. As in the Skinner box test, rats undernourished during only one period occu pied intermediate positions. This is taken to indicate that, with respect to these two measures of behavior, the effects of undernutrition in the fetal and suckling periods were additive. Evidence for an additive effect on physical brain growth is confined to fore- brain DNA-P content, which was substantially reduced by both periods of growth retardation. Cerebellum DNA-P and weights of cerebellum and forebrain were all much more affected by the postnatal treatment. J. Nutr. 103: 1327-1338, 1973.

An analysis of the learning deficit following hyoscine administration to man.

Abstract: 1. Twelve volunteer subjects completed a free-recall word learning test, a number-colour association test, and a scanning task after the following treatments: saline 1 ml, hyoscine 0.4 mg, or atropine 0.6 mg, administered by intravenous injection.2. Performance on all three tests was not significantly impaired after atropine.3. Performance on the two learning tests but not on the scanning task, was significantly impaired after hyoscine.4. Analysis of the results of the free-recall word learning test indicates that impairment of learning following hyoscine does not affect recall over intervals of a few seconds, but affects that portion of the learning curve which has been attributed to long-term (or secondary) rather than short-term (or primary) memory.5. The results suggest that hyoscine 0.4 mg may impair learning processes, without significantly depressing other psychological functions, and that the impairment of learning following hyposcine does not affect recall over intervals memory.

A matrix technique for constructing slip‐line field solutions to a class of plane strain plasticity problems

Abstract: A procedure is described for solving plane strain rigid perfect-plasticity problems which lead to linear integral equations. The problem of finding the initial characteristic (slip-line), from which the complete field can be constructed, is reduced to a simple matrix inversion. Although the form of this matrix will depend on the particular problem concerned, it will be expressible in terms of a few fundamental matrices which occur in all problems of this type. The properties of these basic matrices and FORTRAN subroutines for assimilating them and for performing the corresponding linear transformations are given in detail. In illustration the procedure is applied to a drawing and to a strip rolling problem.

The nature and logic of the peasant economy 1: A Generalisation 1

Abstract: This article discusses the major specific aspects of a general type of peasant economy: the family farm production‐consumption unit, the village as an economic organisation, the market and money in the peasant economy, the political economy of peasant societies. It concludes with an examination of the differing ideas of analysts who agree on the existence of a specific peasant economy but disagree on the relative importance of its characteristics. The aim is to provide a starting‐point for a systematic discussion of the general, the diverse, the relatively stable and the changeable in peasant economy, and the way in which it is affected by state policies; the latter aspects are dealt with in part II†.

Assessing degree of nasal patency by measuring peak expiratory flow rate through the nose.

Abstract: Peak expiratory flow rate through the nose (PEFR n ) can be measured with a Wright peak flow meter. A function of PEFR n , provisionally called blockage index (BI), is described which correlates closely with nasal airway resistance (NAR) but is independent of total expiratory effort. The method is sensitive, and the apparatus is robust and easily transported.

Exact Multisoliton Solutions of the Self-Induced Transparency and Sine-Gordon Equations

Abstract: We confirm that the previously conjectured $N$-soliton solution of the self-induced-transparency equations is a solution for all $N$. The solution is transformed to give an exact solution of the since-Gordon equation describing multiple collision of $N$ kinks with different velocities. Simple asymptotic forms of both solutions are given.

The description of mammals–2 Limbs and locomotion of terrestial mammals

Abstract: Four separate categories of description relating to limbs and locomotion are recognized. Gross variation in limb structure characterizes descriptions at the ordinal level. Detailed morphology of the external features, and of limb bones, extends diagnosis to the familial and generic levels. The gaits of mammals describe locomotory behaviour. In all of these categories, definitions tend to be imprecise and the terminology to be misapplied. This descriptive terminology is critically reviewed in the light of advancing research and a synthetic framework for ordering future studies is proposed.

Nitrogen metabolism of halophytes ii. nitrate availability and utilization

Abstract: SUMMARY The availability and utilization of nitrate by salt-marsh plants has been studied. All the species examined are able to assimilate nitrate, which appears to be the most important form of nitrogen available on the marsh. Species, from the strand line and lower marsh have higher nitrogen contents and nitrate reductase levels, than those from the upper marsh. Competition between species for nitrate is more important in the upper than lower marsh, because of low nitrate supply. Species such as Armeria maritima, Glaux maritima, Limonium vulgare and Triglochin maritima are able to compete more effectively for nitrate in the upper marsh than Puccinellia maritima, Salicornia europaea, Suaeda maritima, Spergularia media and Spartina×anglica. The results indicate there is an increase in nitrogen supply down the marsh, which may be associated with the input of nitrate during tidal innundation.

The effect of an interfacial layer on minority carrier injection in forward-biased silicon Schottky diodes

Abstract: It is shown that the degree of minority carrier injection in Au-Si junctions can be substantially increased by the inclusion of a thin interfacial layer between the metal and the semiconductor. When a forward voltage is applied to the junction, a part of this voltage is developed across the interfacial layer. This favours the reduction of the barrier height to minority carriers, which tunnel from the metal into the semiconductor. The minority carrier injection current increases at the expense of the majority carrier current. For a given oxide thickness, γ(= Jminority/Jtot) increases with forward bias, approaching a saturation value for a few volts applied to the junction. For a given voltage, γ also shows a variation with interfacial layer thickness, δ, and the present results indicate that an oxide thickness can be chosen to optimise γ. In the case of a gold-silicon junction with an insulating layer of thermally-grown oxide, as δ is increased to 40 A, the saturation value of γ increased from 10 −4 for δ = 10 A through a maximum of 2 × 10−1 for δ ⋍ 30 A. For oxides prepared by r.f. sputtering, the maximum value of γ is 10−1 and occurs for δ ⋍ 80 A. These results are of considerable importance in the improvement of injection luminescence in metal-semiconductor diodes.