Showing papers by "University of Portsmouth published in 2000"

A New approach to the evolution of cosmological perturbations on large scales

Abstract: We discuss the evolution of linear perturbations about a Friedmann-Robertson-Walker background metric, using only the local conservation of energy momentum. We show that on sufficiently large scales the curvature perturbation on spatial hypersurfaces of uniform density is conserved when the non-adiabatic pressure perturbation is negligible. This is the first time that this result has been demonstrated independently of the gravitational field equations. A physical picture of long-wavelength perturbations as being composed of separate Robertson-Walker universes gives a simple understanding of the possible evolution of the curvature perturbation, in particular clarifying the conditions under which super-horizon curvature perturbations may vary.

Adiabatic and entropy perturbations from inflation

Abstract: We study adiabatic ~curvature! and entropy ~isocurvature! perturbations produced during a period of cosmological inflation that is driven by multiple scalar fields with an arbitrary interaction potential. A local rotation in field space is performed to separate out the adiabatic and entropy modes. The resulting field equations show explicitly how on large scales entropy perturbations can source adiabatic perturbations if the background solution follows a curved trajectory in field space, and how adiabatic perturbations cannot source entropy perturbations in the long-wavelength limit. It is the effective mass of the entropy field that determines the amplitude of entropy perturbations during inflation. We present two applications of the equations. First, we show why one in general expects the adiabatic and entropy perturbations to be correlated at the end of inflation, and calculate the cross correlation in the context of a double inflation model with two non-interacting fields. Second, we consider two-field preheating after inflation, examining conditions under which entropy perturbations can alter the large-scale curvature perturbation and showing how our new formalism has advantages in numerical stability when the background solution follows a non-trivial trajectory in field space.

Chaotic inflation on the brane

Abstract: We consider slow-roll inflation in the context of recently proposed four-dimensional effective gravity induced on the world-volume of a three-brane in five-dimensional Einstein gravity. We find significant modifications of the simplest chaotic inflationary scenario when the five-dimensional Planck scale is below about 1017 GeV. We use the comoving curvature perturbation, which remains constant on super-Hubble scales, in order to calculate the spectrum of adiabatic density perturbations generated. Modifications to the Friedmann constraint equation lead to a faster Hubble expansion at high energies and a more strongly damped evolution of the scalar field. This assists slow-roll, enhances the amount of inflation obtained in any given model, and drives the perturbations towards an exactly scale-invariant Harrison-Zel’dovich spectrum. In chaotic inflation driven by a massive scalar field we show that inflation can occur at field values far below the four-dimensional Planck scale, though above the five-dimensional fundamental scale.

Detecting Deceit via Analysis of Verbal and Nonverbal Behavior

Abstract: We examined the hypotheses that (1) a systematic analysis of nonverbal behavior could be useful in the detection of deceit and (2) that lie detection would be most accurate if both verbal and nonverbal indicators of deception are taken into account. Seventy-three nursing students participated in a study about "telling lies" and either told the truth or lied about a film they had just seen. The interviews were videotaped and audiotaped, and the nonverbal behavior (NVB) and speech content of the liars and truth tellers were analyzed, the latter with the Criteria-Based Content Analysis technique (CBCA) and the Reality Monitoring technique (RM). Results revealed several nonverbal and verbal indicators of deception. On the basis of nonverbal behavior alone, 78% of the lies and truths could be correctly classi- fied. An even higher percentage could be correctly classified when all three detec- tion techniques (i.e., NVB, CBCA, RM) were taken into account.

Cosmological dynamics on the brane

Abstract: In Randall-Sundrum-type brane-world cosmologies, the dynamical equations on the three-brane differ from the general relativity equations by terms that carry the effects of embedding and of the free gravitational field in the five-dimensional bulk. Instead of starting from an ansatz for the metric, we derive the covariant nonlinear dynamical equations for the gravitational and matter fields on the brane, and then linearize to find the perturbation equations on the brane. The local energy-momentum corrections are significant only at very high energies. The imprint on the brane of the nonlocal gravitational field in the bulk is more subtle, and we provide a careful decomposition of this effect into nonlocal energy density, flux and anisotropic stress. The nonlocal energy density determines the tidal acceleration in the off-brane direction, and can oppose singularity formation via the generalized Raychaudhuri equation. Unlike the nonlocal energy density and flux, the nonlocal anisotropic stress is not determined by an evolution equation on the brane, reflecting the fact that brane observers cannot in general make predictions from initial data. In particular, isotropy of the cosmic microwave background may no longer guarantee a Friedmann geometry. Adiabatic density perturbations are coupled to perturbations in the nonlocal bulk field, and in general the system is not closed on the brane. But on super- Hubble scales, density perturbations satisfy a decoupled third-order equation, and can be evaluated by brane observers. Tensor perturbations on the brane are suppressed by local bulk effects during inflation, while nonlocal effects can serve as a source or a sink. Vorticity on the brane decays as in general relativity, but nonlocal bulk effects can source the gravito-magnetic field, so that vector perturbations can be generated in the absence of vorticity.

Guidelines for the microbiological quality of treated wastewater used in agriculture: recommendations for revising WHO guidelines

Abstract: Three different approaches for establishing guidelines for the microbiological quality of treated wastewater that is reused for agriculture are reviewed. These approaches have different objectives as their outcomes: the absence of faecal indicator organisms in the wastewater, the absence of a measurable excess of cases of enteric disease in the exposed population and a model-generated estimated risk below a defined acceptable risk. If the second approach (using empirical epidemiological studies supplemented by microbiological studies of the transmission of pathogens) is used in conjunction with the third approach (using a model-based quantitative risk assessment for selected pathogens) a powerful tool is produced that aids the development of regulations. This combined approach is more cost-effective than the first approach and adequately protects public health. The guideline limit for faecal coliform bacteria in unrestricted irrigation (41000 faecal coliform bacteria/ 100 ml) is valid, but for restricted irrigation 410 5 faecal coliform bacteria/100 ml is recommended when adult farmworkers are exposed to spray irrigation. A limit of 410 3 faecal coliform bacteria/100 ml is recommended if flood irrigation is used or children are exposed. The guideline limit for nematode eggs for both types of irrigation is adequate except when conditions favour the survival of nematode eggs and where children are exposed; in these cases it should be reduced from 41 egg/l to 40.1 egg/l.

Development of a novel passive sampling system for the time-averaged measurement of a range of organic pollutants in aquatic environments.

Abstract: A new sampling system has been developed for the measurement of time-averaged concentrations of organic micropollutants in aquatic environments. The system is based on the diffusion of targeted organic compounds through a rate-limiting membrane and the subsequent accumulation of these species in a bound, hydrophobic, solid-phase material. It provides a novel and robust solution to the problem of monitoring in situations where large temporal fluctuations in pollutant levels may occur. Accumulation rates are regulated by choice of diffusion-limiting membrane and bound solid-phase material and have been found to be dependent on the physico-chemical properties of individual target analytes. Two separate prototype systems are described: one suitable for the sampling of non-polar organic species with log octanol/water partition coefficient (log P) values greater than 4, the other for more polar species with log P values between 2 and 4. Both systems use the same solid-phase material (47 mm C18 Empore™ disk) as a receiving phase but are fitted with different rate-limiting membrane materials (polysulfone for the polar and polyethylene for the non-polar analytes). The two systems complement each other and together can be used for sampling a wider range of organic analytes than generally possible using current passive sampling techniques. Calibration data are presented for both devices. In each case, linear uptake kinetics were sustained, under constant conditions, for deployment periods of between 1 and 9 days. The effects of water temperature and turbulence on sampling rates have been quantitatively assessed. The performance of the system was further investigated by means of field exposures for one and two weeks in marine environments where calibrated samplers were used to determine the time-averaged concentrations of the polar biocides diuron and irgarol 1051. The quantitative results obtained using the passive sampler were compared with those obtained using spot sampling.

The outsourcing dilemma: a composite approach to the make or buy decision

Abstract: The decision to outsource a part of an organisation’s activities is often the result of an initiative to realise potential production cost efficiencies. In order to avoid the use of such narrow decision criteria this paper considers the use of a wider array of inputs. Following a review of the literature, a composite outsourcing decision framework is presented. This framework consists of three main components. The first seeks to utilise the unique contextual factors associated with each decision; the second considers the strategic implications of deciding to outsource and the third investigates the traditional cost aspects. The framework is then applied to a case study concerning an engineering organisation which had to decide whether to outsource part of its production facilities. The outcomes suggest that the framework was a useful instrument in assisting management in making this decision, although further work in this area is required.

When no means no

Abstract: Cultural discourses of femininity and women's social role have historically and traditionally been constructed around motherhood. However, recent studies into women's childbearing intentions have revealed an increasing number of women in Western Europe and the United States choosing to remain childless. Thus, a distinction has emerged between cultural discourses on femininity and the experiences of an increasing number of women. This article considers the questions that emerge from this. In particular, to what extent and in what ways might cultural discourses of motherhood and femininity have declined and transformed as women's lives have changed. What might be the implications of this for constructions of femininity and identity in women. Drawing on an empirical study into voluntary childlessness amongst women, this article argues that pronatalist discourses and those that denigrate voluntary childlessness persist despite the considerable changes and increased autonomy experienced by women during the second half of the 20th century. However, through rejecting and resisting discourses that conflate femininity with motherhood, childless women create new discourses that can subvert and transform constructions of femininity. The article concludes that the advent of these new and alternative discourses signify the emergence of a radical feminine identity, distinct and unshackled from motherhood.

Cultural and socio-economic impacts of Mediterranean marine protected areas

Abstract: Summary Marine protected areas (MPAs) may be important for protecting the marine environment, but they may also have substantial socio-cultural impacts about which very little is currently known, or acknowledged. In the Mediterranean, few data are available on the socioeconomic consequences of MPAs. The present study reviews the existing data on MPAs in Spain, France, Italy and Greece. A general increase in tourist activities in Mediterranean MPAs is evident, as are increases in the abundances of larger fish species, although there are no data indicating yields for fisheries increase adjacent to MPAs. A large increase in the number of divers and vessels using MPAs has already had impacts on natural benthic communities as a result of diver damage, mooring and the feeding of large fish by divers. Emphasis has been given in only a few MPAs to promoting public awareness of these impacts. Although the conservation of nature should be considered the fundamental objective of MPAs, neglecting their social, cultural and economic impacts has at times led to poor local consensus, if not hostility. We believe that planning and managing MPAs should be conducted on a multidisciplinary basis. Nonetheless, no single model can be considered valid for the whole Mediterranean. The very variable characteristics of coastal areas, from those of small uninhabited islands to those of cities, require different weightings to be assigned for each factor in order to achieve a durable equilibrium and realize the original objectives of each MPA. Only with such flexibility of management will it be possible to reach a greater understanding of the MPA system and create a lasting consensus in favour of conservation, a consensus which would mean an overwhelming majority of people actively avoiding damaging nature and preventing others from doing so.

Children's everyday deception and performance on false-belief tasks

Abstract: Current theory and experimental research suggests that children's discovery of false beliefs at around 4 years of age allows the development of intentional deception. Anecdotal evidence of earlier lies has been dismissed with the argument that they may be ‘blind’ learned strategies rather than genuine deception. This paper presents two studies of everyday deception in comparison with false-belief task performance in young children. Study 1, a longitudinal study of 24 children, shows that the variety and incidence of everyday deceptions reported by mothers did not relate to success or failure on a battery of false-belief tasks, either between different children or over time in the same children. In Study 2 the deceptions of a 21/2-year-old child over a 6-month period were shown to be varied, flexible, context appropriate and too complex to be ‘blind’ learned strategies. It is argued that children's deceptive skills develop from pragmatic need and situational exigencies rather than from conceptual developments; they may learn to lie in the same way as they learn to speak.

Unsupervised Forward Selection: A Method for Eliminating Redundant Variables

Abstract: An unsupervised learning method is proposed for variable selection and its performance assessed using three typical QSAR data sets. The aims of this procedure are to generate a subset of descriptors from any given data set in which the resultant variables are relevant, redundancy is eliminated, and multicollinearity is reduced. Continuum regression, an algorithm encompassing ordinary least squares regression, regression on principal components, and partial least squares regression, was used to construct models from the selected variables. The variable selection routine is shown to produce simple, robust, and easily interpreted models for the chosen data sets.

Towards a stable numerical evolution of strongly gravitating systems in general relativity: The conformal treatments

Abstract: We study the stability of three-dimensional numerical evolutions of the Einstein equations, comparing the standard ADM formulation to variations on a family of formulations that separate out the conformal and traceless parts of the system We develop an implementation of the conformal-traceless ~CT! approach that has improved stability properties in evolving weak and strong gravitational fields, and for both vacuum and spacetimes with active coupling to matter sources Cases studied include weak and strong gravitational wave packets, black holes, boson stars and neutron stars We show under what conditions the CT approach gives better results in 3D numerical evolutions compared to the ADM formulation In particular, we show that our implementation of the CT approach gives more long term stable evolutions than ADM in all the cases studied, but is less accurate in the short term for the range of resolutions used in our 3D simulations

Self-similar cosmological solutions with a nonminimally coupled scalar field

Abstract: We present self-similar cosmological solutions for a barotropic fluid plus scalar field with Brans-Dicke-type coupling to the spacetime curvature and an arbitrary power-law potential energy. We identify all the fixed points in the autonomous phase plane, including a scaling solution where the fluid density scales with the scalar field's kinetic and potential energy. This is related by a conformal transformation to a scaling solution for a scalar field with an exponential potential minimally coupled to the spacetime curvature, but nonminimally coupled to the barotropic fluid. Radiation is automatically decoupled from the scalar field, but energy transfer between the field and nonrelativistic dark matter can lead to a change to an accelerated expansion at late times in the Einstein frame. The scalar field density can mimic a cosmological constant even for steep potentials in the strong-coupling limit.

Behind the Audit Report: A Descriptive Study of Discussions and Negotiations Between Auditors and Directors

Abstract: This paper presents direct evidence concerning the extent, nature, and outcome of interactions between the two primary parties in the auditor-client relationship — finance directors (FDs) and audit engagement partners (AEPs). A questionnaire instrument is used to elicit the frequency with which, over a three year period, an extensive set of 46 audit and audit-related issues is discussed, is negotiated, and results in a change to either the accounting numbers or disclosures. Three hundred FDs and 307 AEPs of listed UK companies are surveyed, with response rates of 51% and 80%, respectively. Principal findings are that: (i) compliance issues dominate discussions, while accounting and fee issues dominate negotiations; (ii) audit committees generally reduce the level of negotiation and increase the level of discussion, suggesting that the overall degree of confrontation declines; and (iii) in the majority of cases (57%), negotiation results in a change to the financial statements, providing evidence of the auditor's influence on the financial statements.

Dilaton gravity on the brane

Abstract: We derive the four-dimensional field equations for the induced metric and scalar field on the world-volume of a 3-brane in a five-dimensional bulk with Einstein gravity plus a self-interacting scalar field. We calculate the effective four-dimensional gravitational constant and cosmological constant for arbitrary forms of the brane tension and self-interaction potential for the scalar field in the bulk. In addition to the canonical energy-momentum tensor for the scalar field and ordinary matter on the brane, the effective four-dimensional Einstein equations include terms due to the scalar field and gravitational waves in the bulk. We present solutions corresponding to static Minkowski brane worlds and also dynamical Friedmann-Robertson-Walker brane world cosmologies. We discuss the induced coupling of the scalar field to ordinary matter on the brane.

Sector collapse forming at Casita volcano, Nicaragua

Abstract: Catastrophic sector collapse occurs when a volcano becomes structurally unable to support its own load. One process particularly capable of weakening the edifice is hydrothermal activity. It can produce high pore pressures and alter strong rock to clays. Alteration can extend progressively over long periods (>100 yr), allowing deformation to develop slowly before collapse. An important finding is that structures produced by such deformation are recognizable and could permit collapse prediction. We present the case of Casita, Nicaragua, where hydrothermal activity has been weakening the edifice core, causing flank spreading, altering original constructional shape, and steepening flank slopes. One side is slumping outward, producing a crescentic scar with a basal bulge. We identify this feature as the site of a potential sector collapse, with conditions ripe for failure.

Inhibition of the development of microorganisms (bacteria and fungi) by extracts of marine algae from Brittany, France.

Abstract: The inhibitory effects of aqueous, ethanolic and dichloromethane fractions from 16 marine algae from the Atlantic shores of North-East Brittany, France, have been investigated against microorganisms frequently associated with immersed surfaces. The extracts were tested in vitro against isolates of marine fungi, bacteria and yeasts potentially involved at different stages in the formation of biofilms in the sea. The high levels of inhibitory activity of nine extracts against marine fungi and Gram-positive bacteria and their apparent absence of toxicity against larvae of oysters and sea urchins suggests a potential for novel active ingredients.

Introduction – the competency movement: its origins and impact on the public sector

Abstract: This introduction seeks to locate the origins of the competency management in American and British management concerns with declining international competitiveness and the need for more efficient and effective managers. It examines the distinctive American and British approaches and identifies and defines the ideas, concepts and techniques associated with competency in each country. The transfer of these ideas and practices into the public sector accompanied the spread of new public management, which has increased throughout the 1990s. The movement is now an international one prompted by both the OECD and the management consultancy industry. The process of adoption and implementation has tended to be pragmatic and ad hoc but evidence suggests it is now becoming an important vehicle for organisational cultural change. This introduction provides the backdrop for the remaining five articles in this special issue of the journal, which illustrate both developments in theory and practice of competency‐based management within public services.

Use of automatic relevance determination in QSAR studies using Bayesian neural networks.

Abstract: We describe the use of Bayesian regularized artificial neural networks (BRANNs) coupled with automatic relevance determination (ARD) in the development of quantitative structure−activity relationship (QSAR) models. These BRANN-ARD networks have the potential to solve a number of problems which arise in QSAR modeling such as the following: choice of model; robustness of model; choice of validation set; size of validation effort; and optimization of network architecture. The ARD method ensures that irrelevant or highly correlated indices used in the modeling are neglected as well as showing which are the most important variables in modeling the activity data. The application of the methods to QSAR of compounds active at the benzodiazepine and muscarinic receptors as well as some toxicological data of the effect of substituted benzenes on Tetetrahymena pyriformis is illustrated.

Measuring motion on DNA by the type I restriction endonuclease EcoR124I using triplex displacement

Abstract: The type I restriction enzyme EcoR124I cleaves DNA following extensive linear translocation dependent upon ATP hydrolysis. Using protein-directed displacement of a DNA triplex, we have determined the kinetics of one-dimensional motion without the necessity of measuring DNA or ATP hydrolysis. The triplex was pre-formed specifically on linear DNA, 4370 bp from an EcoR124I site, and then incubated with endonuclease. Upon ATP addition, a distinct lag phase was observed before the triplex-forming oligonucleotide was displaced with exponential kinetics. As the distance between type I and triplex sites was shortened, the lag time decreased whilst the displacement reaction remained exponential. This is indicative of processive DNA translocation followed by collision with the triplex and oligonucleotide displacement. A linear relationship between lag duration and inter-site distance gives a translocation velocity of 400+/-32 bp/s at 20 degrees C. Furthermore, the data can only be explained by bi-directional translocation. An endonuclease with only one of the two HsdR subunits responsible for motion could still catalyse translocation. The reaction is less processive, but can 'reset' in either direction whenever the DNA is released.

From full employment to employability: a new deal for Britain’s unemployed?

Abstract: Britain’s New Labour Government has radically shifted its policy aims away from securing traditional full employment towards the improvement of “employability”. This paper briefly assesses what is meant by employability and how the Government has integrated its “supply side” approach to the unemployed with the stricter benefit regime it inherited from its Conservative predecessor. It describes the various New Deal and area‐based employment programmes that have been introduced during an intense phase of policy development and experimentation and outlines the immediate impact they have had. The Government’s long‐term aim is to build on this experience and create a “work‐based welfare state” for all those of working age who receive state benefits. In conclusion, the paper highlights some of the weaknesses of the new strategy and draws out the implications that existing evaluations of active labour market programmes have for the likely impact of the New Deals.