Showing papers by "University of Warwick published in 1982"

Analysis of discrimination mechanisms in the mammalian olfactory system using a model nose.

Abstract: Olfaction exhibits both high sensitivity for odours and high discrimination between them. We suggest that to make fine discriminations between complex odorant mixtures containing varying ratios of odorants without the necessity for highly specialized peripheral receptors, the olfactory systems makes use of feature detection using broadly tuned receptor cells organized in a convergent neurone pathway. As a test of this hypothesis we have constructed an electronic nose using semiconductor transducers and incorporating design features suggested by our proposal. We report here that this device can reproducibly discriminate between a wide variety of odours, and its properties show that discrimination in an olfactory system could be achieved without the use of highly specific receptors.

Morphogenesis versus structuration: on combining structure and action. 1982.

Abstract: The fundamental problem of linking human agency and social structure stalks through the history of sociological theory. Basically it concerns how to develop an adequate theoretical account which deals simultaneously with men constituting society and the social formation of human agents. For any theorist, except the holist, social structure is ultimately a human product, but for any theorist, except advocates of psychologism, this product in turn shapes individuals and influences their interaction. However successive theoretical developments have tilted either towards structure or towards action, a slippage which has gathered in momentum over time. Initially this meant that one element became dominant and the other subordinate: human agency had become pale and ghostly in mid-century functionalism, whilst structure betook an evanescent fragility in the re-flowering of phenomenology. Eventually certain schools of thought repressed the second element almost completely. On the one hand structuralist Marxism and normative functionalism virtually snuffed-out agency-the acting subject became increasingly lifeless whilst the structural or cultural components enjoyed a life of their own, self-propelling or self-maintaining. On the other hand interpretative sociology busily banished the structural to the realm of objectification and facticity-human agency became sovereign whilst social structure was reduced to supine plasticity because of its constructed nature. Although proponents of these divergent views were extremely vociferous, they were also extensively criticized and precisely on the grounds that both structure and action were indispensable in sociological explanation.2 Moreover serious efforts to re-address the problem and to re-unite structure and action had already begun from inside 'the two Sociologies',3 when they were characterized in this manichean way. These attempts emerged after the early sixties from 'general' functionalists,4 'humanistic' marxists5 and from interactionists confronting the existence of strongly patterned conduct.6 Furthermore they were joined in the same decade by a bold attempt

Stochastic Differential Equations on Manifolds

Abstract: A. The title is designed to indicate those particular aspects of stochastic differential equations which will be considered here: these are almost equally valid when the manifold in question is ℝ n (although compactness is often a useful simplifying assumption). In fact one of the main themes here will be that stochastic differential equations, even on ℝ n , induce non-trivial differential-geometric structures and these structures are an important tool in analyzing the behaviour of the solutions of the s.d.e.

On Least Squares Estimation when the Dependent Variable is Grouped

Abstract: This paper examines the problem of estimating the parameters of an underlying linear model using data in which the dependent variable is only observed to fall in a certain interval on a continuous scale, its actual value remaining unobserved. A Least Squares algorithm for attaining the Maximum Likelihood estimator is described, the asymptotic bias of the OLS estimator derived for the normal regressors case and a "moment" estimator presented. A "two-step estimator" based on combining the two approaches is proposed and found to perform well in both an economic illustration and simulation experiments.

On the order of words

Abstract: There is no doubt that the model presented here is incomplete. Many important categories, particularly negation and the adverbials, have been entirely ignored, and the treatment of Tense and the affixes is certainly inadequate. It also remains to be seen how the many constructions that have been ignored here are to be accommodated within the framework that has been outlined. However, the fact that a standard categorial lexicon, plus the four rule schemata, seems to come close to exhaustively specifying the main clause constructions of English, and also seems to explain a number of major constraints on transformations, encourages us to compare the theory with certain alternatives, and to examine its broader implications.

Light-stimulated transcription of genes for two chloroplast polypeptides in isolated pea leaf nuclei.

Abstract: Nuclei isolated from both light-grown and dark-grown leaves of Pisum sativum by Percoll density gradient centrifugation incorporate labelled UTP into RNA when supplemented with the other three nucleoside triphosphates. The RNA is heterodisperse, with transcripts up to at least 25S in size. Among these transcripts are sequences hybridizing to cloned DNA probes for wheat rRNA and two abundant chloroplast polypeptides of Pisum, viz. the small subunit of ribulose bisphosphate carboxylase and a polypeptide of the light-harvesting chlorophyll a/b binding complex. Transcription of small subunit and light-harvesting complex sequences is greater (18-fold and 9-fold, respectively) in nuclei from light-grown leaves than in nuclei from dark-grown leaves. Transcription of ribosomal genes, by contrast, is only doubled by growth in the light. Small subunit and light-harvesting complex sequences transcribed in dark-grown nuclei are not degraded in a 120 min chase. These results suggest that the stimulation of accumulation of small subunit and light-harvesting complex mRNAs by exposure of Pisum seedlings to light is mediated by an increase in transcription rather than by a decrease in RNA degradation.

Biochemistry of the chemolithotrophic oxidation of inorganic sulphur.

Abstract: A historical review is presented of the elucidation of the mechanisms of oxidation of inorganic sulphur compounds and of electron transport in the thiobacilli. A unitary mechanism, consistent with current knowledge, is proposed. The significance of polythionates is discussed. The relations between oxidation mechanisms, substrate-level and electron transport-dependent phosphorylation, energy-dependent NAD+ reduction and efficiency of growth are assessed in order to evaluate the efficiency of energy conservation in different species. The unresolved problems are identified for the benefit of those planning further assaults on the last redoubts of the thiobacilli.

Are Solid Surfaces of Ecological Significance to Aquatic Bacteria

Abstract: Man has long been aware of microbial attachment to solid surfaces in the sea and in freshwaters, as slime layers formed by attached microorganisms and their associated polymers are easily detected by touch. Moreover, such slime layers frequently become a nuisance, or even a serious fouling problem, when they occur on submerged man-made structures, such as ship hulls, platforms, or dams.

Immune interferon release when a cloned cytotoxic T-cell line meets its correct influenza-infected target cell

Abstract: T cells stimulated by mitogens1, specific antigens2, including viral antigens3, and alloantigens4 have been shown to produce immune Interferon (IFN-γ). However, the exact circumstances of induction of IFN-γ in T cells have not yet been established, particularly the precise nature of the cell type producing the Interferon. We have recently described5 the selection and cloning of a BALB/c cytotoxic T(Tc)-cell line (L4) which grows in the presence of T-cell growth factor (TCGF), is Lyt-2 positive and kills H-2d target cells infected with any type A influenza vims. The aim of the present study was to examine whether this cloned cytotoxic T-cell line produced IFN-γ on contact with the appropriate target cell. It was found that small amounts of IFN-γ were produced on co-culture of L4 with target cells, whereas L4 cells on their own released no detectable Interferon. The pattern of antigenic specificity by L4 cells for interferon production resembled the requirements for killing in that Tc cell mediated lysis was restricted to H–2d targets infected with influenza A, but not influenza virus B strains, and interferon production was not prevented by a monoclonal antibody to the virus' haemagglutinin, which does not inhibit cytotoxicity while neutralizing the virus.

Bubble contact angle method for evaluating substratum interfacial characteristics and its relevance to bacterial attachment.

Abstract: A bubble contact angle method was used to determine interfacial free-energy characteristics of polystyrene substrata in the presence and absence of potential surface-conditioning proteins (bovine glycoprotein, bovine serum albumin, fatty acid-free bovine serum albumin), a bacterial culture supernatant, and a bacterial exopolymer. Clean petri dish substrata gave a contact angle of 90°, but tissue culture dish substrata were more hydrophilic, giving an angle of 29° or less. Bubble contact angles at the surfaces exposed to the macromolecular solutions varied with the composition and concentration of the solution. Modification by pronase enzymes of the conditioning effect of proteins depended on the nature of both the substratum and the protein, as well as the time of addition of the enzyme relative to the conditioning of the substratum. The effects of dissolved and substratum-adsorbed proteins on the attachment of Pseudomonas sp. strain NCMB 2021 to petri dishes and tissue culture dishes were consistent with changes in bubble contact angles (except when proteins were adsorbed to tissue culture dishes before attachment) as were alterations in protein-induced inhibition of bacterial attachment to petri dishes by treatment with pronase. Differences between the attachment of pseudomonads to petri dishes and tissue culture dishes suggested that different mechanisms of adhesion are involved at the surfaces of these two substrata.

Error correction mechanisms

Abstract: The interface between economic theory and applied econometrics is often one of uneasy compromise, with the pragmatic justification for many accepted procedures resting on a theoretical base. This paper examines the surprisingly strong arguments that exist in terms of economic theory, for the use of error correction mechanisms in the specification of short run dynamic adjustment. A common heresy exists that while economic theory provides a detailed analysis of comparative static equilibria it can offer no guidance as to the appropriate specification of dynamic adjustment towards an equilibrium. perhaps in consequence it is not uncommon to find examples where the necessary dynamic specification is achieved by "tacking" onto an existing equilibrium specification some relatively ad hoc short run adjustment scheme. The intercession of stochastic arguments in this process is confused and critical implications are frequently ignored in practice, but perhaps more importantly there will typically be no guarantee that the dynamic specification is consistent with the prescribed equilibrium. Consistency in this sense requires that the short run dynamic adjustment be directed by the perceived disequilibrium and that eventual convergence to the equilibrium position be ensured. That two separate theoretical arguments, co-exist within the final specification is the root cause of many difficulties both theoretical and empirical.

Root development of vegetable crops

Abstract: Measurements were made at intervals during the growth of seven different vegetable crops grown on the same soil to find how far root development and crop growth could be described by simply derived equations and to find how far the parameter values varied from crop to crop. For each crop K1 ln W+W, (where W is total plant dry weight, t ha−1 and K1 is equal to 1 t ha−1) was linearly related to time from emergence, as in past experiments. The derived equation % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaciiBaiaac6% gaieaacaWFmbGaa8xpaiaa-ngadaWgaaWcbaGaa8NAaaqabaGccqGH% RaWkcaWFIbWaaSbaaSqaaiaa-PgaaeqaaOGaciiBaiaac6gacaWFxb% acdiGaa4xlaiaa-1gacaWF0baaaa!43A9! $$\ln L = c_j + b_j \ln W - mt$$ where L is total root length per unit area, t is time from emergence, cj and bj are coefficients that depend on the crop (j) and m is a coefficient having the same value for all crops, removed 89.4% of the total variance in ln L. The best fit was obtained with a value of m that implied that about 3% of the root carbon was mineralized each day. Generally the logarithm of root density declined linearly with increasing depth. Most of the variation between the gradients of these relations for the different crops was removed by a single regression against logarithm of total root length. The main discernible differences between species in their rooting patterns were that root length for a given top weight of legumes was about half that of non legumes, that the development of storage roots was associated with a less steep decline in root density with depth than for other crops and that onions were exceptional in that the depth to which their roots penetrated did not change appreciably during much of the growing season. A single linear relationship between root depth and top weight (r 2=0.85) covered all non-leguminous crops except onions and another relationship (r 2=0.80) covered the legumes.

The functional equivalence of imagery and movement.

Abstract: A method of investigating mental imagery is presented which shows that movements and imagery of movements are functionally equivalent. Experiment I uses a short-term-motor-memory linear positioning...

Testing Normality in Econometric Models

Abstract: A specification test based on an Edgeworth expansion is proposed and some of its useful properties are noted. In particular the test has an important additivity property, in that a test for higher-order alternatives simply adds additional, asymptotically independent variates to tests lower order alternatives.

Measurement and simulation of the movement and degradation of atrazine and metribuzin in a fallow soil

Abstract: The movement and persistence of atrazine and metribuzin, in a sandy loam soil following application in spring, was simulated using two models. The first model, based on the physical laws describing water and solute movement and using measured values of soil hydraulic properties, underestimated herbicide mobility in the soil and predicted too rapid drying of the deeper soil layers. The accuracy of the simulations was improved by empirically reducing the measured hydraulic conductivities by a factor of 4. This probably reflects the difficulties of obtaining reliable measurements of soil hydraulic properties. A second and simpler model, which simulated water and herbicide movement using mobile and immobile water categories, accurately predicted soil water contents. It tended to underestimate herbicide movement at short times after application, and to overestimate movement later in the experiments. A comparison of different methods of simulating herbicide degradation showed that prediction of degradation rates in the field from laboratory data can be unsatisfactory with some compounds.

The relationship of participation and effectiveness in strategic planning

Abstract: This paper describes the results of a study focusing on effectiveness and participation in strategic planning and their inter-relationships. The work reported is a comparative study of ten, diverse organizations in the United Kingdom. The paper sets out the frameworks for effectiveness and participation against which the empirical work took place; describes the results of the analysis undertaken; and postulates a number of theories concerning effective planning practice and its relation to participation in the system.

Dilute hydrochloric acid extraction of plant material for routine cation analysis

Abstract: A hazard‐free method of extracting cations from dried plant material using dilute (0.5M) hydrochloric acid has been developed for routine determination of cations in dried plant samples. Previous work1,2 has shown that hydrochloric acid can be used to quantitatively extract cations but the methods are slow and tedious. To develop a faster and less tedious method it was first necessary to ascertain the sensitivity of hydrochloric acid extraction to changes in conditions.

Two-Dimensional Discrete Properties of Random Surfaces

Abstract: Recent work has shown that it is possible to predict surface parameters measured digitally from a surface profile by means of three points on the autocorrelation function. The weakness of this work has been that only one-dimensional parameters have been evaluated. The present contribution extends the theory to include two-dimensional parameters of the surface which are expressed in terms of between four and seven points on the autocorrelation function depending on the type of surface. It is shown that this technique provides an alternative to traditional mapping methods. It is shown also that as a general rule results obtained from the discrete analysis do not converge to those obtained from the continuous theory. The nature and magnitude of the differences between the two approaches are discussed in detail. Finally, the theoretical results are confirmed experimentally and the general significance of discrete methods reviewed.

Taxonomy and evolution of broccoli (Brassica oleracea var. italica)

Abstract: The origin and application of the name broccoli are discussed and a distinction between cauliflower and broccoli is proposed, based on their relative ontogeny at marketable maturity. The history and evolution of broccoli is considered in relation to cauliflower and its diversification into annual and biennial types is discussed. White-sprouting broccoli is considered to be closely related to English winter-hardy cauliflower. Calabrese, though representing only a small part of the italica gene pool, has been the most intensively developed, being currently represented by many cultivars, including F1 hybrids. The potential for breeding new Cape and sprouting broccolis is discussed, and the need to conserve existing genetic variability of existing cultivars within Cape and sprouting broccoli is stressed.

Catastrophe theory in physics

Abstract: Presents a broadly based discussion of 'catastrophe theory,' a mathematical discipline commonly associated with the names of Thom and Zeeman, placing emphasis on the development feedback between the mathematics and its applications, especially to the physical sciences. The author aims to present a typical selection of current work. Among the more prominent of the concepts that have emerged from this work are co-dimension, determinacy, unfoldings and organising centres. He shows, using specific applications as motivation, how these concepts may be used, and generalised to areas not obviously within the formal purview of 'catastrophe theory' as it is often presented. Structural stability, a concept from topological dynamics that provides a philosophical background for catastrophe theory, is also discussed. The mathematics of the subject has advanced considerably over the past decade, and in doing so has lost many of its original limitations. Some of these new directions are exhibited. On occasion, the catastrophe-theoretic methods are compared to more traditional ones.