Showing papers by "Lancaster University published in 1982"

A method of fitting the gravity model based on the poisson distribution

Abstract: In this paper [the authors] suggest an alternative method for fitting the gravity model. In this method the interaction variable is treated as the outcome of a discrete probability process whose mean is a function of the size and distance variables. This treatment seems appropriate when the dependent variable represents a count of the number of items (people vehicles shipments) moving from one place to another. It would seem to have special advantages where there are some pairs of places between which few items move. The argument will be illustrated with reference to data on the numbers of migrants moving in 1970-1971 between pairs of the 126 labor market areas defined for Great Britain.... (EXCERPT)

Compound Poisson Regression Models

Abstract: Count data are easily modelled in GLIM using the Poisson distribution. However, in modelling such data the counts are often aggregated over one or more factors, or important explanatory variables are unavailable and as a result the fit obtained is often poor. This paper examines a method of allowing for this unexplained variation by introducing an independent random variable into the linear model for the Poisson mean, giving a compound Poisson model for the observed data. By assuming a known form for the distribution of this random variable, in particular the normal distribution, and using a combination of numerical integration, the EM algorithm and iteratively reweighted least squares, maximum likelihood estimates can be obtained for the parameters. Macros for implementing this technique are presented and its use is illustrated with several examples.

Survival of mycorrhiza formed by cenococcum geophilum fr. in dry soils

Abstract: SUMMARY Seedlings and 2-year old saplings of Tilia cordata growing in the shade on sandy-textured soils can survive periods when the water potential of the soil decreases to −18 to −55 bars. Their mycorrhiza formed by Cenococcum geophilum is shown to remain alive. Measurement of rates of water-loss from seedlings in similar conditions decreases from 16.0 to 26.2 mg h−1 when the soil is wet, to 4.1 to 4.6 mg h−1 when the soil is dry. Calculation of the volume of the mycorrhiza shows that its water content would support transpiration for periods not exceeding 1 h. Survival of the mycorrhiza through long periods of drought is apparently related to the ability of the fungal partner to withstand desiccation.

A review of lava flow processes related to the formation of lunar sinuous rilles

Abstract: This paper reviews processes which, it is argued, occurred in lunar lava flows and were involved in the formation of lunar sinuous rilles.

Explosive volcanic eruptions — V. Observations of plume dynamics during the 1979 Soufrière eruption, St Vincent

Abstract: Summary. During the 1979 eruption of the Soufritre of St Vincent, West Indies, a 14min period of explosive activity occurred on April 22. The first three minutes of this activity were filmed. Five individual explosions formed distinct plumes which fed an eruption column which eventually ascended to a height of over 18 km. The ascent velocities of the fronts of these plumes ranged from 8.5 to 61.7m s-'. The half-angle of spreading of the plume fronts ranged from 21.5 to 24". One of the plumes was observed to 8 km height and decelerated steadily from 5 1.5 to 23 m s-l. The main column fed by individual explosions was, however, observed to accelerate from 8.5 to 58 m s-l in the same height interval. A theoretical treatment of volcanic plume motion is presented. Measurements of dimensions, velocities and spreading rates from the film are used to estimate plume parameters such as temperature, particle content and volume discharge rate of magma from the theoretical relationships. These calculations show that the individual plumes became hotter and richer in juvenile ash with time. The acceleration of the main eruption column was the result of being fed by increasingly hotter and more ash-rich explosions. An average volume discharge rate of 12600m3s-' is estimated from the analysis of the plume motions. This value agrees closely with an estimate of discharge rate based on the heat flux required to form an 18 km high column. This agreement suggests that theories of convective motions in plumes can be successfully adapted to the volcanic case, as long as the effect of hot entrained ash particles is considered.

Vision and proprioception in simple catching.

Abstract: Articular proprioception is normally considered to provide accurate information about limb position, particularly in ball skills in which the eyes are thought to be occupied with tracking the ball....

Leaf appearance and extension in field-grown winter wheat plants: the importance of soil temperature during vegetative growth

Abstract: Mainstem leaf appearance and leaf extension were monitored at 7-day intervals throughout the vegetative development of field-grown winter wheat plants, during two growing seasons 1977–9. Using hourly air and soil temperature records, it was found that the rate of leaf appearance was controlled by soil temperature, with the best linear relationships being obtained using accumulated soil temperature above a base temperature of 0 °C at 1 and 5 cm depth. Leaf appearance could be predicted equally well using 09.00 G.M.T. screen air temperatures although deviations from each linear relationship were found during very cold periods when slow leaf extension rates delayed leaf appearance.Leaf extension was also found to be linearly related to temperature, with the best fit being obtained using accumulated soil temperature above 2·5 °C at 5 cm depth, suggesting a threshold of 2·5 °C for leaf extension. The response to temperature (extension per unit of accumulated temperature) was the same for all the leaves of a given plant, or sowing date; however, the fact that the rate of leaf extension increased progressively with sowing date suggests that plant response to temperature may be determined at crop emergence (possibly mediated by rate of change of day length). Leaf extension rates could be predicted satisfactorily using 09.00 G.M.T. soil temperatures (5 or 10 cm) but less so using screen air temperatures.The prediction of plant leaf areas or crop leaf area indices using such relationships between temperature and leaf growth was found to be hampered by rapid and irregular rates of leaf senescence.

Bioenergetic and Ultrastructural Changes Associated with Chloroplast Development

Abstract: Publisher Summary This chapter discusses the bioenergetic and ultrastructural changes associated with chloroplast development. During development, large amounts of lipids, pigments, proteins, and nucleic acid are synthesized and transformed, requiring expenditure of energy. The chapter discusses these biosynthetic demands in relation to ultrastructure, the appearance of photophosphorylation, and the various control mechanisms involved in the regulation of these events. It also describes the plastid development in different systems. The semicrystalline structure is remarkable in appearance and phototransformation. The chapter outlines the storage reserves and mobilization during plastid development in different systems. The claims of ultrastructural associations between organelles, especially plastids and mitochondria, are fraught with problems. Close appressions of plastids and mitochondria are often observed in all groups of algae. The polypeptide composition of the plastid envelope membranes differs from that of the mitochondrial membranes, the endoplasmic reticulum, and the internal thylakoids. The chapter discusses the formation of pigments, lipids, and the photochemical systems during chloroplast morphogenesis. Various aspects of chloroplast development are directly or indirectly initiated, maintained, or terminated by light and hormones.

Learning the ropes

Abstract: B ecause educational institutions have been acknowledged as playing an important role in social control and the acquisition of values, aspects of education that might otherwise be treated as given come in for closer scrutiny. The decision-making process within the classroom, the power structure of the institution, and the institution's relationship with employing organizations become of at least as much interest as the curriculum to the researcher. The way the curriculum is formulated, what is included and excluded, the extent of its specialization or integration, and its implicit priorities are as important in understanding its function as the subject matter which it comprises. The connection between education and the workplace, school and industry, is not in doubt. The design of curricula and the scope of examinations are influenced by perceptions of future occupational or professional requirements. Leaders of industry and commerce are represented on the governing bodies of the institutions responsible for promoting educational research and teacher training. There is constant pressure for education at all levels to be relevant to the needs of the workplace as defined by management. In industrial training, the link between education and work is even more direct. Training policy is designed to meet specific organizational requirements. Systems of accountability ensure that training codes and curricula are closely adhered to. Yet it is not always clear precisely how this link is forged or how it works in practice. Industrial training, whether for apprentices, shop stewards, supervisors, or managers, is within the ultimate control of senior management. The content and method of training programs are intended to support the company mission and to develop the skills and knowledge believed appropriate to its tasks. Equally, it is through training that employees learn the behavior expected of them if they are to be accepted as trustworthy and effective members of the work force. Thus training reinforces the values that underlie the culture of the organization. E.H. Schein, in comparing induction programs with the coercive persuasion experienced by prisoners of war, wrote: New members must also be taught to be loyal and productive, which is tantamount to saying that they must accept the ideology, participate actively, and refrain from resistance or sabotage.

Differential abaxial and adaxial stomatal responses to indole‐3‐acetic acid in commelina communis l.

Abstract: Summary The responses of abaxial and adaxial stomata to indole-3-acetic acid (IAA) were examined on isolated epidermis of Commelina communis. IAA was remarkably effective in producing wide adaxial apertures accompanied by a massive increase in the stomatal K+ content, and, therefore, eliminating the normal disparity in both the opening and K+ accumulation between abaxial and adaxial stomatal cells; it also reversed the suppressive effect of abscisic acid. IAA may affect the transport of K+ either directly or indirectly through its control of the proton pump. If the IAA-induced adaxial opening and K+ accumulation is a result of a stimulation of proton extrusion, then, under normal conditions, the proton pump should operate at a lower capacity in adaxial than in abaxial guard cells. Alternatively, the lack of stomatal sensitivity to IAA in the presence of Na+ ions suggests a possibility that it might have a direct effect on the K+ transport. In either case, as reported here, an external supply of IAA would enhance K+ accumulation in adaxial guard cells. The inherent disparity in opening and accompanied K+ accumulation between abaxial and adaxial stomatal cells is postulated to be a result of differences in endogenous auxin level between the two epidermes and/or of differential adaxial and abaxial sensitivity to auxin. Thus, the results indicate a hormonal basis for the differential adaxial and abaxial opening.

Growth effects of SO 2 and/or NO 2 on woody plants and grasses during spring and summer

Abstract: The two most widespread air pollutants in Britain are SO2 and NO2 (refs 1, 2). These not only contribute to acidity in rain3, which may seriously affect plant growth, but also cause substantial effects by their direct action as gaseous pollutants. Research into the effects of the gaseous pollutants on grasses has shown that the combination of SO2 and NO2 may be particularly toxic to plant growth4,5. Further research in this laboratory showed that Phleum pratense L. was more sensitive to SO2 when growth was slow and it was suggested that exposures during winter may be particularly phytotoxic6. Here we present the results of experiments in which serious effects on plant growth were detected even during the summer months. Autumn-sown smooth stalked meadow grass (Poa pratensis L.) exposed to SO2 or SO2 plus NO2 showed marked growth reductions during the winter and spring, and although the plants recovered during the summer, flowering was inhibited. Moreover, four broad-leaved tree species showed substantial decreases in growth when exposed to SO2 plus NO2 between March and August.

Fine structure of mycorrhiza formed by cenococcum geophilum fr. on tilia cordata mill

Abstract: SUMMARY Mycorrhizas formed by Cenococcum geophilum were collected from seedlings of Tilia cordata growing on sandy soil in which the water content was only 2 to 3 % of dry mass (equivalent to water potentials of − 18 to − 55 bars). The fine structure of the mycorrhiza shows that the majority of cells of the fungal mantle, of the bristle-like extended hyphae and of the root contain living protoplasts with organelles of normal appearance. The mantle and Hartig net are compact tissues (synenchyma) and the outer cells of the mantle and the extended hyphae have thick walls in which the outer electron-opaque layer has a microfibrillar structure. Hyphal septa in the Hartig net, mantle and extended hyphae are electron-transparent and have simple pores with Woronin-bodies. Cells of the root, adjacent to the Hartig net, contain high densities of mitochondria but there is no penetration of intracellular fungal structures (haustoria). There is a well-defined zone of tannin-cells.

Gender and Occupational Stratification

Abstract: In modem Britain, as in most known societies, gender is a central feature of the social division of labour i; some tasks are socially defined as 'men's work' and others are considered to be Vomen's work'. While the sex-typing of tasks is less rigid in advanced capitalist societies than in some others (some men do feminine' jobs and a few women do 'masculine' worî X and despite the fast-changing labour process and occupational structure, sexual divisions remain a central feature of the social division of labour. In this paper I contend that gender is of crucial in:q>ortance, not only in assigning people to 'places' in the division of labour, but also in the very definition of occupations, and thereby in shaping the division of labour as a whole. The social relations of gender ̂ are central to the labour process. As such, gender must be included as a central feature of any analysis of social stratification, whether it is concerned with the social charaaehstics of people in particular occupations or whether it seeks to analyse the social relations in which they engage. The present discussion will be confined to the realm of paid worl^ although (as I have argued elsewhere) die scope d stratification studies must eventually be broadened to include unpaid work also, before the sexual divison of labour and the sodal relations of gender can be given due impomnce.' Within the sphere of formal, paid enjoyment; there remains a high degree of segregation by sex, and most jobs are considered to be better suited to one or other sex. These 'men's jobs' and 'women's jobs' have become so defined throitgh a variety of ^wdfic historical pnxxMCS. The sexual division of labour hts altered akM^ with the sodal division of labour as a whole; similarly, sodal definitions as to the suitability of men or women fat peffionniog different tasks have

Institutional Mythologies and Dual Societies in the Management of Risk

Abstract: The risk assessment fraternity is well aware by now of the limited role played by various “technical”, “rational”, or “analytical” approaches to risks in real decision making contexts*. Reactions to this news vary from the familiar technocratic lament about the irrational ways of the world outside their rational bastions, to the vigorous celebration of the political and psychological “underworlds” which impose those limits on the technocratic perspective. Eschewing these polarized extremes, however, most people in the field are still working out their responses, as are those like myself who are really marginal to it, and who came with an already well developed experience of the sociological dimensions and instrumental limitations of scientific rationality. Given that reactions are still in the formulative stage; given the centrality of the idea of scientific rationality in risk assessment philosophies and methodologies (and in modern policy making generally); and given that appropriate responses are of practical importance in policy making; I shall attempt in this paper to outline some reasons why the sociological analysis of scientific rationality that has developed to some maturity in the last few years is directly relevant to the kinds of questions now facing risk assessment when it attempts to define where it should be heading next. In the process I shall outline some areas of research under the general area of risk assessment of technology politics that this different perspective suggests. There is a potentially important though as yet unrealized correspondence between many of the insights from the psychological research which has influenced risk analysis and the sociological analysis of scientific rationality. In presenting the latter my aim is not to upstage the former but to point out how the naturally individualistic learnings of psychology can and must be developed into sociological and anthropological frameworks for formulating questions and possibilities. If there is one central concern of this paper it is the following.

Nitrogen fixation in the temperate estuarine intertidal sediments of the River Lune

Abstract: Abstruct In situ measurements of acctylenc reduction in undisturbed temperate intertidal estuarine sediments show that activity occurs from late spring to early autumn and amounts to an annual rate of 1.4 kg of N fixed per hectare. The low rates are caused by the combination of low temperatures, high salinities, and a shortage of carbon substrates for heterotrophic nitrogenfixing bacteria. The main contributing organisms are the sulf:lte-reducers and salinity-tolerant strains of KZebsieZZn pneumonine. Other nitrogen-fixing bacteria (photosynthetic bacteria, salinity-tolerant strains of Azotobacter &roococcunz, and cyanobacteria) arc present only in low numbers or are unable to fix nitrogen at the salinities found in the sedirncnts. Morecambe Bay comprises large areas of tidal flats (sediments) off the northwest coast of England. The relative uniformity of the flats makes them ideal as an experimental site for the in situ measurement of acetylene reduction. The sediments are soft enough to allow insertion of hollow cylinders without disturbing the particle distribution and moist enough

Stomatal behaviour and water movement through roots of wheat plants treated with abscisic acid

Abstract: Experiments with isolated roots of wheat plants suggested that when water uptake rates are low, low concentrations of abscisic acid (ABA) may increase the flux of water into roots. This increase was recorded despite an ABA-stimulated reduction in the hydraulic conductance of the whole root system. Hydraulic conductances were measured under steady-state conditions. A system is described where the stomatal behaviour and water movement through roots of a single intact plant may be concurrently monitored. Experiments with intact plants confirmed that application of ABA could increase the rate of water movement into roots when uptake rates were low. No such increase was observed at high flux rates. Application of ABA to roots caused partial stomatal closure and caused conductance to oscillate around a reduced mean value. An ABA-stimulated increase in the turgor sensitivity of stomata is postulated and the significance of this effect is discussed.