Showing papers by "University of Warwick published in 1993"

Treatment of complicated mourning

Abstract: This is the first book to focus specifically on complicated mourning, often referred to as pathological, unresolved, or abnormal grief. It provides caregivers with practical therapeutic strategies and specific interventions that are necessary when traditional grief counseling is insufficient. ""The goal is to turn 'complicated' into 'uncomplicated' mourning."" Rando examines the unique issues in bereavement situations that put mourners at high risk for complicated mourning. She synthesizes the literature and integrates it with specific treatment approaches.

Coupled Nonlinear Oscillators and the Symmetries of Animal Gaits

Abstract: Animal locomotion typically employs several distinct periodic patterns of leg movements, known as gaits. It has long been observed that most gaits possess a degree of symmetry. Our aim is to draw attention to some remarkable parallels between the generalities of coupled nonlinear oscillators and the observed symmetries of gaits, and to describe how this observation might impose constraints on the general structure of the neural circuits, i.e. central pattern generators, that control locomotion. We compare the symmetries of gaits with the symmetry-breaking oscillation patterns that should be expected in various networks of symmetrically coupled nonlinear oscillators. We discuss the possibility that transitions between gaits may be modeled as symmetry-breaking bifurcations of such oscillator networks. The emphasis is on general model-independent features of such networks, rather than on specific models. Each type of network generates a characteristic set of gait symmetries, so our results may be interpreted as an analysis of the general structure required of a central pattern generator in order to produce the types of gait observed in the natural world. The approach leads to natural hierarchies of gaits, ordered by symmetry, and to natural sequences of gait bifurcations. We briefly discuss how the ideas could be extended to hexapodal gaits.

The lux autoinducer regulates the production of exoenzyme virulence determinants in Erwinia carotovora and Pseudomonas aeruginosa.

Abstract: Erwinia carotovora and Pseudomonas aeruginosa secrete exoenzymes that contribute to the pathogenesis of plant and mammalian infections respectively. E.carotovora mutants defective in synthesis of the pectinase, cellulase and protease exoenzymes were isolated and classified into two groups. Group 2 mutants were found to be defective in the production of a small freely diffusible molecule, N-3-(oxohexanoyl)-L-homoserine, lactone (HSL), and were avirulent. Addition of exogenous HSL to these group 2 mutants restores synthesis of the exoenzymes and virulence in planta. Of the exoenzymes of P.aeruginosa the metalloprotease, elastase, is an established virulence determinant. Mutants of P.aeruginosa that are defective in elastase production have been isolated and were again found to fall into two groups. Analogous to the group 2 mutants of E.carotovora, group 2 mutants of P. aeruginosa are defective in the synthesis of HSL and exogenous HSL restores elastase production. HSL has now been linked to the control of bioluminescence in Vibrio fischeri, carbapenem antibiotic production of E.carotovora and the above exoenzyme virulence determinants. This information significantly enhances our understanding of the extent and nature of pheromone mediated gene expression control in prokaryotes.

From international system to international society: structural realism and regime theory meet the English school

Abstract: The idea of international society is an essential element in the study of international relations. International society is the core concept of the English school and has not yet been systematically integrated with American-originated structural realism and regime theory. This article brings together these three bodies of theory and shows how they complement and strengthen each other. It uses structural realism to show that international society is, like balance of power, a natural product of anarchic international relations and not, as some in the English school assume, only a result of exceptional historical circumstances. This line of analysis establishes definitional criteria for international society that enable a clear boundary to be drawn between international systems with and without international societies. It also shows how state-based international society relates to individual-based world society and supports an argument that in advanced systems, this relationship becomes complementary, not contradictory. The resulting theoretical synthesis provides an essential historical and political-legal foundation for regime theory, showing that international society is both the intellectual forebear and the necessary condition for the development of regimes. Connection strengthens all three bodies of theory and opens up useful channels that connect realist and liberal thinking. One result is that international society can be used both to conceptualize the complexities of a contemporary global international system, with its network of regimes ordered in terms of concentric circles, and to sketch out a policy-relevant research agenda for understanding it.

Rapid DNA extraction protocol from soil for polymerase chain reaction‐mediated amplification

Abstract: A simple and rapid method of DNA extraction from soil was developed and DNA was made suitable for subsequent efficient amplification by the polymerase chain reaction (PCR). Key features of the extraction and purification were cold lysozyme- and SDS-assisted lysis with either freezing-thawing or bead beating, cold phenol extraction of the resulting soil suspension, CsCl and KAc precipitation and, finally, spermine-HCl or glass milk purification of DNA. Crude DNA preparations contained 4–20 μg DNA per g of soil extracted, and at least 50% of this was recovered in the final purified DNA preparations. The resulting DNA was pure enough to be restricted by various enzymes, and was amplifiable at concentrations of up to 20 ng of soil-derived DNA per 50 μl reaction mix. Amplification of a 683 bp target sequence, pat, was performed with different Taq DNA polymerases. Application of the protocol enabled us to detect target DNA derived from roughly 103 introduced Pseudomonas fluorescens (RP4 :: pat) cfu per g of soil. The fate of an introduced population in the soil could be followed to this limit with PCR-assisted detection of target DNA. In addition, target DNA was detected in soil 5 months after release, when the introduced organism was no longer detectable on selective agar plates. The extraction and purification protocol applied to various different soil types resulted in DNA of sufficient purity to permit amplification by PCR.

Metaphor in Political Discourse: The Case of the `Common European House'

Abstract: The metaphor of the `common European house' appeared in political discourse in several European languages in the late 1980s. Political discourse, usually treated in a domestic single-language persp...

Modelling the probability of leaving unemployment: competing risks models with flexible base-line hazards

Abstract: SUMMARY Unemployment durations are generally modelled by using survival analysis. In the past, in Britain, all such studies have not only used very restrictive parametric specifications of the hazard functions, most commonly Weibull in form, but also only modelled unemployment durations without distinguishing the nature of the exit. These restrictions potentially bias the estimated effects, particularly those of the time varying economic variables and the base-line hazard. When we use semiparametric methods to estimate models with completely unrestricted base-line hazards, we find the restrictions implied by the Weibull specification to be rejected for Britain. We then use a competing risks model to distinguish exit into a job from other exits. We find that the single-risk model of exit understates the effects of income in and out of work on the probability of entering a job.

Direct observation of magnetic flux lattice melting and decomposition in the high-Tc superconductor Bi2.15Sr1.95CaCu2O8+x

Abstract: The flux line lattice inside a single crystal of Bi2.15Sr1.95CaCu2O8+x has been observed using small-angle neutron diffraction. The diffracted intensity goes rapidly to zero at a magnetic-field-dependent flux lattice melting temperature; this melting coincides with the appearance of finite resistance within the superconducting state. The flux lattice signal can also be made to disappear at low temperatures, by applying a sufficiently high field, probably because of the decomposition of flux lines into two-dimensional 'pancake' vortices.

Analogical Reasoning and Knowledge Generation in Organization Theory

Abstract: This paper reviews and evaluates the cognitive status to which metaphors and analogies have been ascribed in the process of knowledge generation in organiza tion theory. Three perspectives are identified: metaphors as ways of thinking, metaphors as dispensable literary devices, and metaphors as potential ideological distortions. The main tenets of each one of them are reviewed and subsequently submitted to criticism. It is argued here that, despite their differing claims, the preceding perspectives converge on the assumption that there is a gap between metaphorical and scientific languages. The grounds for the existence of this gap are challenged in this paper, noting that the structure-mapping theory of analogy provides a methodology for developing metaphorical insights to yield scientific models and theories.

Synthesis and resolution of 1-(2-diphenylphosphino-1-naphthyl)isoquinoline; a PN chelating ligand for asymmetric catalysis.

Abstract: A multistep synthesis resulting in a good yield of the title compound has been developed based on the Pd-catalysed coupling of 1-chloroisoquinoline and 2-methoxy-1-naphthylboronic acid (5). The product is converted into the corresponding trifluoromethanesulphonate (10) by successive demethylation and treatment with (CF3CO)2O, followed by a further Pd-catalysed coupling with Ph2P(O)H. The resulting phosphine oxide (11) was cleanly reduced with HSiCl3. Resolution of the phosphinamine (4) was carried out with the Pd complex derived from (R)-(+)-dimethyl(1-(1-naphthyl)ethyl)amine and PdCl2; the diastereomers were of different stabilities and solubilities and were therefore readily separated. The resolved phosphinamine, [α]D22 ± 153 (c = 1, CHCl3), was enantiomerically stable on heating to 65°C for 24h. X-ray crystal structures of the adduct (16) and the Pd dimer (7) isolated during the initial coupling reaction are presented.

A novel strategy for the isolation of luxI homologues : evidence for the widespread distribution of a LuxR:LuxI superfamily in enteric bacteria

Abstract: The pheromone N-(3-oxohexanoyl)-L-homoserine lactone (OHHL) regulates expression of bioluminescence in the marine bacterium Vibrio fischeri, the production of carbapenem antibiotic in Erwinia carotovora and exoenzymes in both E. carotovora and Pseudomonas aeruginosa. A characteristic feature of this regulatory mechanism in V. fischeri is that it is cell density-dependent, reflecting the need to accumulate sufficient pheromone to trigger the induction of gene expression. Using a lux plasmid-based bioluminescent sensor for OHHL, pheromone production by E. carotovora, Enterobacter agglomerans, Hafnia alvei, Rahnella aquatilis and Serratia marcescens has been demonstrated and shown also to be cell density-dependent. Production of OHHL implies the presence in these bacteria of a gene equivalent to luxI. Chromosomal banks from all five enteric bacteria have yielded clones capable of eliciting OHHL production when expressed in Escherichia coli. The luxI homologue from both E. carotovora (carI) and E. agglomerans (eagI) were characterized at the DNA sequence level and the deduced protein sequences have only 25% identity with the V. fischeri LuxI. Despite this, carI, eagI and luxI are shown to be biologically equivalent. An insertion mutant of eagI demonstrates that this gene is essential for OHHL production in E. agglomerans.

A Comparison of Regression Analysis and Data Envelopment Analysis as Alternative Methods for Performance Assessments

Abstract: This paper compares regression analysis and data envelopment analysis as two alternative methods for assessing the comparative performance of homogeneous organizational units such as bank branches or schools The comparison is restricted to units using a single resource or securing a single output It focuses on the estimates of relative efficiency, marginal input-output values and target input-output levels that the two methods offer A set of hypothetical hospitals is used to illustrate the performance of the two methods It is found that, in general, data envelopment analysis outperforms regression analysis on accuracy of estimates but regression analysis offers greater stability of accuracy

Autoregulation of carbapenem biosynthesis in Erwinia carotovora by analogues of N-(3-oxohexanoyl)-L-homoserine lactone

Abstract: N-(3-Oxohexanoyl)-L-homoserine lactone (HSL) (I) is the autoregulator controlling carbapenem antibiotic biosynthesis in Erwinia carotovora ATCC 39048. The chemical synthesis and biological evaluation of analogues of HSL are described. These include alterations of chirality, side-chain modifications, ring size and ring hetero atom. A number of compounds are reported which are capable of restoring the phenotype to a HSL negative mutant but at higher concentrations than HSL. A-factor, the autoregulator of streptomycin biosynthesis in Streptomyces griseus, was not active as an inducer of carbapenem biosynthesis in E. carotovora.

Analysis and reduction of vibration and acoustic noise in the switched reluctance drive

Abstract: This paper describes the results of an extensive study into the production and reduction of acoustic noise and vibration in the switched reluctance drive. Time domain analysis has been used to draw conclusions about the effects of changing the operating parameters of the power electronic controller on the vibration and acoustic noise. Experimental results have been taken from a four-phase switched reluctance drive with one-, two-, or four-phase excitation. The results of this time domain study reveal important information about the stator vibration which would not be apparent from frequency spectra. The results have been used to derive operational concepts for the power electronic controller to reduce the acoustic noise and vibration produced by the drive. A new control technique has been developed to cancel the stator vibration. Using this novel control method, experimental results show that the vibration and acoustic noise produced by a switched reluctance drive can be reduced dramatically without affecting the performance of the drive.

Isolation and Molecular Characterization of Five Marine Cyanophages Propagated on Synechococcus sp. Strain WH7803.

Abstract: Five marine cyanophages propagated on Synechococcus sp. strain WH7803 were isolated from three different oceanographic provinces during the months of August and September 1992: coastal water from the Sargasso Sea, Bermuda; Woods Hole harbor, Woods Hole, Mass.; and coastal water from the English Channel, off Plymouth Sound, United Kingdom. The five cyanophage isolates were found to belong to two families, Myoviridae and Styloviridae, on the basis of their morphology observed in the transmission electron microscope. DNA purified from each of the cyanophage isolates was restricted with a selection of restriction endonucleases, and three distinguishably different patterns were observed. DNA isolated from Myoviridae isolates from Bermuda and the English Channel had highly related restriction patterns, as did DNA isolated from Styloviridae isolates from Bermuda and the English Channel. DNA isolated from the Myoviridae isolate from Woods Hole had a unique restriction pattern. The genome size for each of the Myoviridae isolates was ca. 80 to 85 kb, and it was ca. 90 to 100 kb for each of the Styloviridae isolates. Southern blotting analysis revealed that there was a limited degree of homology among all cyanophage DNAs probed, but clear differences were observed between cyanophage DNA from the Myoviridae and that from the Styloviridae isolates. Polypeptide analysis revealed a clear difference between Myoviridae and Styloviridae polypeptide profiles, although the major, presumably structural, protein in each case was ca. 53 to 54 kDa. Images

Neutralization of Animal Viruses

Abstract: 1 Introduction.- 2 Immunoglobulin G Neutralization by Inhibition of Attachment of Virus to the Cell.- 3 Immunoglobulin G Neutralization Which Does Not Inhibit Attachment of Virus to the Cell.- 4 Immunoglobulin G Neutralization by Aggregation of Virions . ..- 5 Immunoglobulin G Neutralization Mechanisms which Operate After Attachment of the Virus-Antibody Complex to a Cell Receptor Unit.- 5.1 Inhibition of Fusion at the Plasma Membrane.- 5.2 Inhibition of Endocytosis.- 5.3 Inhibition of Fusion of Viral and Cellular Membranes.- 5.4 Inhibition of Non-fusion Uncoating.- 5.5 Inhibition of Events which Occur After Primary Uncoating.- 6 Neutralization which Occurs by Virus Binding Antibody After It Has Attached to a Cell.- 7 Role of the Cell in Neutralization.- 8 Antibody-Dependent Enhancement of Infectivity by Neutralizing Antibody: Fc and Complement Receptors.- 9 Neutralization by Polymeric Immunoglobulin A.- 10 Neutralization by Immunoglobulin M.- 11 The Relevance of Immunoglobulin Isotype to Neutralization.- 12 Viral Carbohydrates, Proteins and Neutralization.- 12.1 Carbohydrates and Neutralization.- 12.2 Proteinsand Neutralization.- 13 Properties of Protein and Peptide Antigens Which Elicit Neutralizing Antibody.- 14 Neutralization In Vivo.- 15 Complement and Neutralization.- 16 Neutralization by Inhibition of Release of Progeny Virus from the Infected Cell.- 17 Changes in Virus Proteins and Virion Structure on Binding Antibody, Including Synergistic Neutralization.- 18 Reversibility of Neutralization.- 19 Neutralization by Fragments of Antibody.- 20 Quantitative Aspects of Neutralization.- 21 Unconventional Neutralization.- 21.1 Genetic Engineering of Antibodies and Viruses.- 21.2 Anti-idiotype Antibodies and Neutralization.- 22 The Evolutionary Significance of Neutralization Sites.- 22.1 Why Do Viruses Have Neutralization Sites?.- 22.2 Strategies which Avoid or Minimize Expression of, or Response, to Neutralization Sites.- 22.2.1 Relating to the Virus Particle.- 22.2.2 Relating to the Immune System.- 23 Neutralization of Poliovirus and Rhinovirus: A Summary.- 23.1 Introduction.- 23.2 Attachment.- 23.3 Internalization.- 23.4 Post-internalization.- 23.5 Aggregation.- 23.6 Conformational Changes on Binding Antibody.- 24 Neutralization of Type a Influenza Virus by Immunoglobulins M, A and G: A Summary.- 24.1 Introduction.- 24.2 IgM Neutralization.- 24.3 IgA Neutralization.- 24.4 IgG Neutralization.- 24.5 Discussion.- 25 Neutralization of HIV-1: A Summary.- 26 Conclusions.- References.

Hexapodal gaits and coupled nonlinear oscillator models

Abstract: The general, model-independent features of different networks of six symmetrically coupled nonlinear oscillators are investigated. These networks are considered as possible models for locomotor central pattern generators (CPGs) in insects. Numerical experiments with a specific oscillator network model are briefly described. It is shown that some generic phase-locked oscillation-patterns for various systems of six symmetrically coupled nonlinear oscillators correspond to the common forward-walking gaits adopted by insects. It is also demonstrated that transitions observed in insect gaits can be modelled as standard symmetry-breaking bifurcations occurring in such systems. The present analysis, which leads to a natural classification of hexapodal gaits by symmetry and to natural sequences of gait bifurcations, relates observed gaits to the overall organizational structure of the underlying CPG. The implications of the present results for the development of simplified control systems for hexapodal walking robots are discussed.

Area-interaction point processes

Abstract: We introduce a new Markov point process that exhibits a range of clustered, random, and ordered patterns according to the value of a scalar parameter. In contrast to pairwise interaction processes, this model has interaction terms of all orders. The likelihood is closely related to the empty space functionF, paralleling the relation between the Strauss process and Ripley'sK-function. We show that, in complete analogy with pairwise interaction processes, the pseudolikelihood equations for this model are a special case of the Takacs-Fiksel method, and our model is the limit of a sequence of auto-logistic lattice processes.

In Search of HRM

Abstract: HRM has been the industrial relations issue of the 1980s and early 1990s. Although it has very few direct references to HRM, WIRS3 sheds considerable light on a number of the debates involved. Not only does it suggest that some of the ideas and practices associated with HRM appear to be taking root; its most striking, and paradoxical, findings are that these fragments of HRM are to be found in union rather than non-union workplaces. These findings have considerable implications for policy and practice as well as for future WIRSs.

How does the benefit effect vary as unemployment spells lengthen

Abstract: SUMMARY This paper investigates how the effect of income while unemployed on the probability of an individual leaving unemployment varies with the length of time that the individual has been unemployed. We examine this question in the context of a variety of alternative econometric models. We extend the Proportional Hazards model with unrestricted baseline hazard to one in which there are unrestricted effects of a subset of the explanatory variables and also consider models that can be estimated as series of binary response models The proportional hazard restrictions are rejected for the sample of British unemployed men analysed and in the binary sequence framework Logit and Probit models based on symmetric distributions dominate (in likelihood terms) the Extreme Value form model implied by extension of the Proportional Hazards formulation. Logit models with a flexible form for the duration dependence which also incorporate unobserved heterogeneity in a flexible way are estimated. The results for all formulations indicate a rapidly declining effect of unemployment income as a spell lengthens, with no significant effect for the long-term unemployed. The preferred specifications which allow for omitted heterogeneity indicate no significant effect after about 5 months, and this result is robust to the inclusion or exclusion of previous labour-market experience variables and to the choice of mixing distribution.

Phonological activation of semantic competitors during lexical access in speech production

Abstract: Experimental evidence from picture-naming tasks suggests that lexical access in speech production (lexicalisation) occurs in two non-overlapping stages. Semantic information is used to access an abstract lexical form; only when this stage is complete does phonological realisation begin. Such experimental data are interpreted as evidence against connectionist models of lexicalisation. This paper argues that, counterintuitively, connectionist models are not inconsistent with these data. This proposal is supported by appropriate simulations. Interactive activation models of speech production have the additional advantage of accounting for speech error and other data.

The general concept of molecular chaperones

Abstract: This introductory article proposes a conceptual framework in which to consider the information that is emerging about the proteins called molecular chaperones, and suggests some definitions that may be useful in this new field of biochemistry. Molecular chaperones are currently defined in functional terms as a class of unrelated families of protein that assist the correct non-covalent assembly of other polypeptide-containing structures in vivo, but which are not components of these assembled structures when they are performing their normal biological functions. The term assembly in this definition embraces not only the folding of newly synthesized polypeptides and any association into oligomers that may occur, but also includes any changes in the degree of either folding or association that may take place when proteins carry out their functions, are transported across membranes, or are repaired or destroyed after stresses such as heat shock. Known molecular chaperones do not convey steric information essential for correct assembly, but appear to act by binding to interactive protein surfaces that are transiently exposed during various cellular processes; this binding inhibits incorrect interactions that may otherwise produce non-functional structures. Thus the concept of molecular chaperones does not contradict the principle of protein self-assembly, but qualifies it by suggesting that in vivo self-assembly requires assistance by other protein molecules.

Manufacturing and the Convergence Hypothesis: What the Long-Run Data Show

Abstract: The commonly accepted chronology for comparative productivity levels, based on GDP data, does not apply to the manufacturing sector, which shows evidence of a much greater degree of stationarity of comparative labor productivity performance among the major industrialized countries of Britain, Germany, and the United States. These results for manufacturing suggest that convergence of GDP per worker must have occurred through trends in other sectors and through compositional effects of structural change. The persistent, large labor productivity gap between the United States and Europe cannot be explained simply by differences in capital per worker, but is related to technological choice.

Trading forward in an imperfect market: the case of electricity in britain*

Abstract: The thrust of government policy in the British electricity industry has been to create a competitive and transparen t commodity market To this end there has been a separation of supply from distribution and an independent company operates a transparent spot market, known as the pool However, there is also a set of futu res and options-style contracts which lie over the pool that are not transparent This paper considers the effects of the contract market on the pool The model is an application of the theory of futures-style trading when the spot market is imperfect However, the model is somewhat non-standard as there is no secondary trading in the contra cts and the generators may capture rents in the contract market The results suggest several externalities due to the strategic use of th ese contracts by both the generators and the RECs which may limit the number of contracts traded It is argued that the Office for Electricity Regulation (Offer) should intervene to help the creation of a transparent and standardized contract market This may ensure the success of the contract market, ease entry to generation and foster competition Copyright 1993 by Royal Economic Society