Showing papers by "University of Warwick published in 1992"

A calculus of mobile processes, II

Abstract: We present the a-calculus, a calculus of communicating systems in which one can naturally express processes which have changing structure. Not only may the component agents of a system be arbitrarily linked, but a communication between neighbours may carry information which changes that linkage. The calculus is an extension of the process algebra CCS, following work by Engberg and Nielsen, who added mobility to CCS while preserving its algebraic properties. The rr-calculus gains simplicity by removing all distinction between variables and constants; communication links are identified by names, and computation is represented purely as the communication of names across links. After an illustrated description of how the n-calculus generalises conventional process algebras in treating mobility, several examples exploiting mobility are given in some detail. The important examples are the encoding into the n-calculus of higher-order functions (the I-calculus and combinatory algebra), the transmission of processes as values, and the representation of data structures as processes. The paper continues by presenting the algebraic theory of strong bisimilarity and strong equivalence, including a new notion of equivalence indexed by distinctions-i.e., assumptions of inequality among names. These theories are based upon a semantics in terms of a labeled transition system and a notion of strong bisimulation, both of which are expounded in detail in a companion paper. We also report briefly on work-in-progress based upon the corresponding notion of weak bisimulation, in which internal actions cannot be observed. 0 1992 Academic Press, Inc.

The Character and Significance of Strategy Process Research

Abstract: This essay discusses the character and significance of strategy process research. Process research in strategic management is paradigmatically diverse and empirically complex. Strategy process research has been narrow in its focus and its undoubted contribution has sometimes been obscured by the lack of explicit discourse about its analytical foundations. The essay draws on a wide range of social science ideas to lay out a set of internally consistent insights and assumptions to guide thinking and empirical inquiry about the analysis of process issues in strategic management. The essay also provides a guide to the eight papers contained in this special issue.

On studying managerial elites

Abstract: The study of managerial elites is one of the most important, yet neglected areas of social science research. This paper synthesizes and critically reviews three intellectual traditions in the study of managerial elites. These are: interlocking directorates and the study of institutional and societal power, the study of boards and directors, and the composition and correlates of top management teams. The paper concludes by arguing for the development of a complementary research tradition which combines a contextual and processual analysis of managerial elites.

Putting giddens into action: social systems and managerial agency

Abstract: This article examines the influence of Anthony Giddens on recent work in management studies, especially the contribution of his structurationist pers- pective to understanding managerial agency. A citation analysis and discussion of prominent exponents such as Ranson et al. (1980), Andrew Pettigrew and Hugh Willmott, concludes that Giddens' influence is substantial but lopsided. Giddens' concern for the intersection and tension between different social systems has been particularly neglected. Drawing on the insights of current 'institutionalist' studies of societal influences on organizations, the article builds a structurationist account of managerial agency that is founded on the contradictions within and between different social systems. The article ends by considering the implications of this structurationist account for current concerns with managerial leadership, organizational symbolism and strategic choice.

Racks and links in codimension two

Abstract: A rack, which is the algebraic distillation of two of the Reidemeister moves, is a set with a binary operation such that right multiplication is an automorphism. Any codimension two link has a fundamental rack which contains more information than the fundamental group. Racks provide an elegant and complete algebraic framework in which to study links and knots in 3–manifolds, and also for the 3–manifolds themselves. Racks have been studied by several previous authors and have been called a variety of names. In this first paper of a series we consolidate the algebra of racks and show that the fundamental rack is a complete invariant for irreducible framed links in a 3–manifold and for the 3–manifold itself. We give some examples of computable link invariants derived from the fundamental rack and explain the connection of the theory of racks with that of braids.

Morse theory for periodic solutions of hamiltonian systems and the maslov index

Abstract: In this paper we prove Morse type inequalities for the contractible 1-periodic solutions of time dependent Hamiltonian differential equations on those compact symplectic manifolds M for which the symplectic form and the first Chern class of the tangent bundle vanish over q(M). The proof is based on a version of infinite dimensional Morse theory which is due to Floer. The key point is an index theorem for the Fredholm operator which plays a central role in Floer homology. The index formula involves the Maslov index of nondegenerate contractible periodic solutions. This Maslov index plays the same role as the Morse index of a nondegenerate critical point does in finite dimensional Morse theory. We shall use this connection between Floer homology and Maslov index to establish the existence of infinitely many periodic solutions having integer periods provided that every I-periodic solution has at least one Floquet multiplier which is not equal to 1.

Wages, Profits and Rent-Sharing

Abstract: The paper uses CPS data from 1964 to 1985 to test for the existence of rent-sharing in US tabor markets, Using an unbalanced panel from the manufacturing sector, and random-effects and fixed-effects specifications, the paper finds that changes in wages are explained by movements in lagged levels of profitability and unemployment. The results appear to be consistent with rent-sharing theory (or a labor contract framework with risk-averse firms) and to be inconsistent with the competitive labor market model. The paper estimates the unemployment elasticity of pay at approximately -0.03, and the profit elasticity of pay at between 0.02 and 0.05.

Output growth and the British industrial revolution: a restatement of the Crafts‐Harley view

Abstract: n the early i98os we published revised estimates of aggregate economic performance during the British industrial revolution which have stimulated reappraisal of the beginnings of modern economic growth.2 These new estimates have led most scholars to abandon the previous orthodoxy which had been based on the pioneering work of Deane and Cole.3 We have subsequently explored further aspects of the industrial revolution using our i982/3 estimates of the rate of growth as acceptable best guesses.4 Recently, however, several papers published in this journal have, with varying degrees of hostility, expressed doubts about our estimates.5 We think it is now opportune to respond to these comments. Our critics have questioned the appropriateness of our estimation techniques and have suggested that our overall view of the industrial revolution is misconceived. While we do not wish to dismiss the points that have been made, we feel both that many of the specific criticisms of our estimating techniques have been erroneous and that our overall view of the late eighteenth and early nineteenth centuries has been misunderstood. Initially in section I we present a brief summary of a coherent new view of British growth that emerged from our aggregate estimates. The bulk of the paper then takes up the technical issues that have recently been raised. In particular, we argue the following main points. First, that there is inevitably a range of possible estimates for industrial output growth given the inherent index number and data problems. Both Crafts's and Harley's original estimates fall within this range, as do Jackson's new estimates, whereas Deane and Cole's do not. Second, that we do not accept Jackson's case for preferring what he calls a Crafts rather than a Harley view of industrial output growth nor do we accept his dismissal of the indices of industrial output presented by Crafts, Leybourne, and Mills (CLM) and by Harley. Third, that Hoppit and Berg and Hudson substantially overstate

Unfamiliar face recognition in relatively able autistic children.

Abstract: Two experiments were carried out assessing autistic children's recognition, discrimination, and fixation of unfamiliar faces and unfamiliar buildings. The experiments showed that (i) unfamiliar face recognition is impaired relative to normal peers, non-verbal ability matched and verbal ability matched controls. Relative to verbal ability matched controls (ii) recognition of buildings is normal; (iii) there is an enhanced discrepancy between face discrimination and buildings discrimination, in favour of buildings; and (iv) fixation is normal. Analysis of the results suggests that impaired face recognition does not result from impaired attention or discrimination.

Group Child Interviews as a Research Tool

Abstract: Group interviews have several advantages over individual interviews. In particular they help to reveal consensus views, may generate richer responses by allowing participants to challenge one another's views, may be used to verify research ideas or data gained through other methods and may enhance the reliability of children's responses. There are, however, difficulties in carrying out group interviews and they require skilful and sensitive guidance by the interviewer. There have been few reports of their use with primary‐aged children but the work reported here suggests that they are a viable and useful technique with that age group.

N-(3-oxohexanoyl)-L-homoserine lactone regulates carbapenem antibiotic production in Erwinia carotovora.

Abstract: Erwinia carotovora A.T.C.C. 39048 produces the antibiotic 1-carbapen-2-em-3-carboxylic acid. A number of mutants with a carbapenem-non-producing phenotype were selected as part of an investigation into the molecular and genetic basis of carbapenem biosynthesis. Cross-feeding studies revealed that the mutants fell into two discrete groups. Group 1 mutants were found to secrete a diffusible low-molecular-mass compound which restored carbapenem production in group 2 mutants. This compound was isolated from the spent culture supernatant of a group 1 mutant using solvent extraction, hydrophobic-interaction chromatography and silica-gel chromatography, and finally purified by reverse-phase semipreparative h.p.l.c. M.s. and n.m.r. spectroscopy revealed that the compound was N-(3-oxohexanoyl)homoserine lactone. Both D- and L-isomers were synthesized, and subsequent analysis by c.d. established that the natural product has the L-configuration. Although carbapenem production was restored by both isomers, dose-response curves indicated that the L-isomer has greater activity, with an induction threshold of about 0.5 micrograms/ml. N-(3-Oxohexanoyl)-L-homoserine lactone is, therefore, an autoregulator of carbapenem biosynthesis rather than a biosynthetic intermediate. This compound is already known for its role in autoinduction of bioluminescence in the marine bacterium Vibrio fischeri. It is also structurally-related to the A- and I-factors which are known to regulate production of antibiotics in some Streptomyces species. Its association in this work with the regulation of carbapenem biosynthesis implies a broader role for autoregulator-controlled gene expression in prokaryotes.

Scanning electrochemical microscopy. 12. Theory and experiment of the feedback mode with finite heterogeneous electron-transfer kinetics and arbitrary substrate size

Abstract: The theory of the feedback mode of the scanning electrochemical microscope (SECM) is extended to include the cases of both finite heterogeneous electron-transfer (et) kinetics at the substrate and arbitrary substrate sizes. Theoretical treatments are developed using two independent approaches: (i) the formulation and numerical solution of multidimensional integral equations and (ii) the alternating direction implicit finite-difference method. Working curves and tabulated data are presented for both quasi-reversible and irreversible et reactions on the substrate

After Orientalism: Culture, Criticism, and Politics in the Third World

Abstract: Over the last decade, studies of ‘third world’ histories and cultures have come to draw to a very considerable extent upon the theoretical perspectives provided by poststructuralism and postmodernism. With the publication in 1978 of Edward Said's work, Orientalism, these perspectives—now fused and extended into a distinctive amalgam of cultural critique, Foucauldian approaches to power, engaged ‘politics of difference,’ and postmodernist emphases on the decentered and the heterogeneous—began to be appropriated in a major way for the study of non-European histories and cultures. Certainly in our own field of Indian colonial history, Said's characteristic blending of these themes has now become virtually a paradigm for a new generation of historians and anthropologists. These directions have been most recently and sharply endorsed in Gyan Prakash's discussion, ‘Writing Post-Orientalist Histories of the Third World: Perspectives from Indian Historiography.’

The Dynamics of n Weakly Coupled Identical Oscillators

Abstract: We present a framework for analysing arbitrary networks of identical dissipative oscillators assuming weak coupling. Using the symmetry of the network, we find dynamically invariant regions in the phase space existing purely by virtue of their spatio-temporal symmetry (the temporal symmetry corresponds to phase shifts). We focus on arrays which are symmetric under all permutations of the oscillators (this arises with global coupling) and also on rings of oscillators with both directed and bidirectional coupling. For these examples, we classify all spatio-temporal symmetries, including limit cycle solutions such as in-phase oscillation and those involving phase shifts. We also show the existence of “submaximal” limit cycle solutions under generic conditions. The canonical invariant region of the phase space is defined and used to investigate the dynamics. We discuss how the limit cycles lose and gain stability, and how symmetry can give rise to structurally stable heteroclinic cycles, a phenomenon not generically found in systems without symmetry. We also investigate how certain types of coupling (including linear coupling between oscillators with symmetric waveforms) can give rise to degenerate behaviour, where the oscillators decouple into smaller groups.

The influence of ethylene in plant tissue culture

Abstract: Ethylene produced by plant tissues grown in vitro may accumulate in large quantities in the culture vessels, particularly from rapidly growing non-differentiated callus or suspension cultures, and hence is likely to influence growth and development in such systems. Research into this aspect of tissue culture has been sparse, although it has grown recently with the increasing importance of in vitro regeneration. This review deals with the measurement and relevance of the accumulated ethylene, and the influence of both exogenous and endogenous ethylene in the different types of tissue culture systems. The relationships between ethylene and other growth regulators in tissue culture growth and development are also discussed. Although in some cases its influence seems negligible, in many types of tissue culture ethylene may act either as a promoter or inhibitor depending on the species used. Thus ethylene has an important influence on many aspects of in vitro regeneration, but it is also clear that we cannot at present describe a specific role or roles for ethylene in tissue culture which can be applied at a general, species-wide level. If its effects are to be enhanced or diminished in order to improve the efficiency and range of plant tissue culture, then more research is needed to clarify what its fundamental role might be in in vitro growth and development.

Rehabilitating the industrial revolution

Abstract: Rehabilitating the industrial revolution. Gradualist perspectives now dominate economic and social histories of the industrial revolution. Analyses of economic change which rely on growth accounting and macroeconomic estimates of productivity indicate continuity with the past; social historians have followed in turning aside from the analysis of new class formations. This article challenges these perspectives. Currently accepted economic indicators and recent social history underplay the extent and uniqueness of economic and social transformation. The article emphasizes change in technology, the use of a female and child labour force, regional specialization, demographic behaviour, and political change.

Application of an electronic nose to the discrimination of coffees

Abstract: An investigation has been carried out into the response of an array of twelve tin oxide sensors to the headspace of coffee packs. Discriminant and classification function analyses are performed on the array response to each of three commercial coffees (covering two different blends and two roasts) as well as one coffee which has been subjected to a range of six roasting times. Multivariate functions are calculated from the entire data set (90 samples) or alternatively using half of it, to permit cross-validation. A success rate of 89.9% is achieved with the former procedure in classifying the three commercial coffee odours directly from the response (change in sensor conductances) of the array. This value falls to 81.1% when half of the data set is used for cross-validation. Preprocessing the array data, by normalizing the response of each sensor over the array, is found to increase the success rate (to 95.5%) on the entire data set only. The effect on coffee odour of a set of six roasting times (zero to 11.5 min) is also investigated and found to be considerable, some sensors registering an increase in conductance by a factor of three. A 100% group classification is achieved with zero and long roasting times, the overall success rate being 88.1%. The main conclusion is that tin oxide gas sensors can be used to discriminate between both the blend and roasting level of coffee, confirming their potential application in an electronic instrument for on-line quantitative process control in the food industry.

Free radical processes and loss of seed viability during desiccation in the recalcitrant species Quercus robur L.

Abstract: SUMMARY Loss of moisture in mature seeds of Quercus robur L. was associated with loss of viability, a rise in lipid peroxidation and build-up of free radicals. Radical-initiated damage was largely confined to the embryonic axes as their moisture contents declined to below 47 %. The accumulation of a stable free radical in axial tissue, detected by electron para-magnetic resonance (EPR), was indistinguishable from the EPR response previously shown in a moss on droughting and maize roots on desiccation. A minor higher-field component appeared to represent an intermediate stage in the sequence of free radical reactions associated with loss of water. Using seeds from freshly abscised fruits dried to different moisture contents, protective mechanisms against activated forms of oxygen were monitored in cotyledons and in embryonic axes. The two tissues exhibit distinctly different molecular defences against oxidative attack; that in the cotyledons being predominantly enzymatic, with relatively high and increasing activities of superoxide dismutase and glutathione reductase; that in the axes being largely through the anti-oxidants, ascorbic acid and alpha-tocopherol. We conclude that a decrease in enzymic protection against oxidative attack in the axes, associated with diminishing concentrations of alpha-tocopherol (and depletion of the precursor gamma-tocopherol) as moisture was lost, was directly linked with lipid peroxidation and free radical formation in the axes and that these events taken together may contribute to loss of viability in these recalcitrant seeds.

The Use of Soft Systems Methodology in Practice

Abstract: This paper reports the results of a survey intended to discover the extent to which Checkland's Soft Systems Methodology (SSM) is used in practice. Some 300 questionnaires were sent to people who had had some exposure to SSM and, surprisingly, nearly half were returned. The majority described in detail their uses of SSM and most felt that it had been successful. This paper describes the overall quantitative results from the survey as well as presenting a qualitative analysis of the experiences of using SSM.

The Woman of Legal Discourse

Abstract: Feminist socio-legal theory has been developing in exciting and controversial ways over the last twenty years. The developments that lawyers can see almost certainly parallel developments in feminist thought elsewhere. But feminist socio-legal theory faces another difficulty in as much as the tension that has always existed around the issue of whether to try to 'use' law for 'women' has taken on a new shape. Law is undoubtedly sexist at one level. The problem with these approaches is that the meaning of differentiation tends to become collapsed into the meaning of discrimination and the fulcrum of the argument rests with the idea that women are treated badly in law because they are differentiated from men. The idea that 'law is male' arises from the empirical observation that most lawmakers and lawyers are indeed male. Woman has always been both kind and killing, active and aggressive, virtuous and evil, cherishable and abominable, not either virtuous or evil.

Personality disorder and self-wounding.

Abstract: At least 1 in 600 adults wound themselves sufficiently to need hospital treatment. More men than women do it, although more women receive psychological treatment. Many have a history of sexual or physical abuse. Self-wounding differs from other self-harm in being aimed neither at mutilation nor at death. Self-wounding coerces others and relieves personal distress. Repeated self-wounding is one criterion of borderline personality disorder but we prefer to consider it an 'addictive' behaviour rather than an expression of a wider disorder. Psychological management may need to be augmented by drug or social treatment. Carers, including professional carers, usually need help to contain the turbulence that self-wounding produces.

Odour discrimination with an electronic nose

Abstract: Smell is probably the least understood and exploited of the principal human senses, yet it is clearly important to both product and process control in many industries, such as foodstuffs, beverages, tobacco and perfumery. Advances in the field of integrated microelectronic devices have led to new instruments, robots, capable of vision and complex touch or taction, but not yet of smell. This paper reviews the research effort that has been carried out at Warwick University over recent years into the development of an electronic instrument that can mimic the human sense of smell. The approach that we have adopted is to construct a microprocessor-controlled system comprising an array of solid-state chemical gas sensors (with overlapping partial sensitivities to odorants) and associated signal processing and pattern recognition. This electronic system is based upon our present knowledge of the biological system. Our earliest electronic nose consisted of an array of only three to twelve tin dioxide thick-film sensors, yet it can discriminate between alcohols, beverages, tobacco blends and coffees. Current efforts are reported towards the fabrication of an integrated microsensor metal oxide array, the development of other electronic devices using polymeric materials, and the implementation of various pattern-recognition techniques, including correlation, principal-component analysis, cluster analysis and artificial neural networks. Finally, the application areas most likely to arouse widespread interest in the next decade are discussed.

Partial Metric Spaces

Abstract: Scott models are topological models of complete partial orders used for Tarskian fixed point semantics of the lambda calculus. As of yet there are no methods for deriving Scott models from specifications of the "complete" objects beyond an arbitrary choice. This paper introduces "partial metrics" for generalising a theory of complete objects into a Scott model including partial objects.

Scanning Electrochemical Microscopy. 17. Studies of Enzyme-Mediator Kinetics for Membrane= and Surface- Immobilized Glucose Oxidase

Abstract: The scanning electrochemical microscope (SECM) can be used to detect electron-transfer reactions of tlp-generated species that occur at nonconductlve surfaces contalnlng a redox-actlve enzyme. Experlments were carrkd out wlth glucose oxldase lmmoblilzed on several substrates and the apparent kinetics of the enzyme catalyds were measured for several medlator oxldants under condltlons of hlgh pgiucose concentration. Theory for the SECM feedback current was developed to model the llmltlng zero- and flrst-order eiectrontransfer klnetlcr expected for such surface catalyds. Working curves relatlng the SECM feedback current to surface rate constants are presented. For Substrates wlth glucose OXC dam covalently attached to the surface or trapped wlthln a porous membrane, the enzyme reactlon was readlly detected and the SECM feedback currents measured at low mediator concentration (ca. 50 pM) were found to excluslvely flt the model for zeroorder heterogeneous kinetlcs. However, at low enzyme surface concentratlon or wlth extendve chemlcal crorrJinklng of immoblllzed glucose oxidase, It was very difficult to use the SECM to detect and quanttfy the enzyme reactlon. General guideilnes for studylng enzyme surface reactions with the SECM are given, and the prospects for detecting and klneticaily assaying enzymes of cellular, and even subcellular, samples are discussed.

Shaping Strategic Change: The Case of the NHS in the 1980s

Abstract: This article explores the question of why the management of change has become an issue in the National Health Service (NHS). It reports the results of a study which explored reasons for variability in the observed rate and pace of strategic service change in the NHS. The metaphor of ‘receptive’ and ‘non‐receptive’ contexts for change is introduced and eight ‘signs and symptoms’ of receptivity outlined. Some examples are presented. These results give us a logic and language which may enable us to understand processes of change in the NHS.

Employment Flexibility and Human Resource Management: The Case of Three American Electronics Plants:

Abstract: This paper critically examines management's recruitment of temporary labour at three U.S. electronics firms operating in the Republic of Ireland. Recent discussions around the flexible firm and hum...