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Showing papers by "Brunel University London published in 1998"


Journal ArticleDOI
TL;DR: The evidence, from both laboratory and field studies, that exposure to steroid hormone mimics may impair reproductive function is reviewed and the weight of evidence for endocrine disruption in wildlife is critically assessed.
Abstract: In recent years, a number of man-made chemicals have been shown to be able to mimic endogenous hormones, and it has been hypothesized that alterations in the normal pattern of reproductive development seen in some populations of wildlife are linked with exposure to these chemicals. Of particular importance are those compounds that mimic estrogens and androgens (and their antagonists), because of their central role in reproductive function. In fact, the evidence showing that such chemicals actually do mimic (or antagonize) the action of hormones in the intact animal is limited. In only a few cases have laboratory studies shown that chemicals that mimic hormones at the molecular level (in vitro) also cause reproductive dysfunction in vivo at environmentally relevant concentrations. In addition, the reported studies on wild populations of animals are limited to a very few animal species and they have often centered on localized 'hot-spots' of chemical discharges. Nevertheless, many of these xenobiotics are persistent and accumulate in the environment, and therefore a more widespread phenomenon of endocrine disruption in wildlife is possible. This article reviews the evidence, from both laboratory and field studies, that exposure to steroid hormone mimics may impair reproductive function and critically assesses the weight of evidence for endocrine disruption in wildlife.

1,077 citations


Journal ArticleDOI
TL;DR: It is shown that many of the so-called 'environmental oestrogens' also possess anti-androgenic activity, demonstrating that hormone-mimicking chemicals can have multiple hormonal activities, which may make it difficult to interpret their mechanisms of action in vivo.
Abstract: There is presently considerable interest in endocrine disruption which is a new area of endocrinology concerned with chemicals that mimic hormones, in particular sex steroids. It has been hypothesised that exposure to such chemicals may be responsible for adverse effects in both humans and wildlife. Until now, chemicals that mimic oestrogens (so-called xenoestrogens) have been the main focus of endocrine disruption research. However, recent evidence suggests that many abnormalities in the male reproductive system may be mediated via the androgen receptor. By blocking androgen action, exposure to an anti-androgen may cause changes similar to those associated with oestrogen exposure. We have used in vitro yeast-based assays to detect oestrogenic, anti-oestrogenic, androgenic and anti-androgenic activities in a variety of chemicals of current interest. We show that many of the so-called 'environmental oestrogens' also possess anti-androgenic activity. The previously reported anti-androgenic activities of vinclozolin and p,p'-1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene (DDE) were confirmed. We also found that o,p'-1,1,1,-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT), bisphenol A and butyl benzyl phthalate were anti-androgenic. However, not all xenoestrogens are also anti-androgenic, because nonylphenol was found to be a weak androgen agonist. Our results demonstrate that hormone-mimicking chemicals can have multiple hormonal activities, which may make it difficult to interpret their mechanisms of action in vivo. Although not a specific objective of this study, our results also demonstrate that yeast-based assays are powerful tools with which to investigate both agonist and antagonistic hormonal activities of chemicals.

842 citations


Journal ArticleDOI
TL;DR: Findings from in vitro and in vivo studies which confirm that a range of alkyl hydroxy benzoate preservatives (parabens) are weakly estrogenic are reported, suggesting that the safety in use of these chemicals should be reassessed.

698 citations


Journal ArticleDOI
TL;DR: Analysis of a candidate gene (SURF1) of unknown function revealed several mutations that suggest a role for SURF1 in the biogenesis of the COX complex and define a new class of gene defects causing human neurodegenerative disease.
Abstract: Leigh Syndrome (LS) is a severe neurological disorder characterized by bilaterally symmetrical necrotic lesions in subcortical brain regions that is commonly associated with systemic cytochrome c oxidase (COX) deficiency. COX deficiency is an autosomal recessive trait and most patients belong to a single genetic complementation group. DNA sequence analysis of the genes encoding the structural subunits of the COX complex has failed to identify a pathogenic mutation. Using microcell-mediated chromosome transfer, we mapped the gene defect in this disorder to chromosome 9q34 by complementation of the respiratory chain deficiency in patient fibroblasts. Analysis of a candidate gene (SURF1) of unknown function revealed several mutations, all of which predict a truncated protein. These data suggest a role for SURF1 in the biogenesis of the COX complex and define a new class of gene defects causing human neurodegenerative disease.

593 citations


OtherDOI
01 Jul 1998
TL;DR: In this paper, the behaviour of the limits surface defined by a recursive division construction can be analyzed in terms of the eigenvalues of a set of matrices, and suggestions for the further improvement of the method are made.
Abstract: The behaviour of the limits surface defined by a recursive division construction can be analysed in terms of the eigenvalues of a set of matrices. This analysis predicts effects actually observed, and leads to suggestions for the further improvement of the method.

490 citations


Journal ArticleDOI
TL;DR: In this article, the authors provide a comprehensive review for those who are interested in using optical diagnostics for in-cylinder soot and combustion temperature measurement in diesel engines, including laser induced incandescence (LII) and light scattering.

435 citations


Journal ArticleDOI
TL;DR: In this article, a genetic algorithm is applied to the problem of determining the optimal hourly schedule of power generation in a hydrothermal power system with a nonlinear relationship between water discharge rate, net head and power generation.
Abstract: A genetic algorithm is applied to the problem of determining the optimal hourly schedule of power generation in a hydrothermal power system. A multi-reservoir cascaded hydroelectric system with a nonlinear relationship between water discharge rate, net head and power generation is considered. The water transport delay between connected reservoirs is also taken into account. The main control parameters that affect the genetic algorithm performance are discussed and a summary of the theoretical basis of the genetic algorithm method is presented. It is shown that a multiple step genetic algorithm search sequence can provide the optimal hourly loading of the system generators.

332 citations


Journal ArticleDOI
TL;DR: Low concentrations of oestradiol and oestrone, similar to the reported concentrations in effluent, have profound effects on male fish, causing greater vitellogenin synthesis and testicular inhibition.

326 citations


Journal ArticleDOI
TL;DR: There is now unequivocal evidence that a wide variety of chemicals capable of disrupting the endocrine system are present in the aquatic environment, and how wide-ranging these adverse effects are is assessed to determine their severity at the population level.

277 citations


Journal ArticleDOI
01 Dec 1998-Polymer
TL;DR: In this paper, the authors investigated the relationship between various parameters of superabsorbent polymers, including the ultimate degree of absorption and rate of absorption, and the ratio of crosslinker to monomer for different polymerisation systems.

260 citations



Journal ArticleDOI
TL;DR: Choice of approach rests on weighing the more invasive nature of CABG against the greater risk of recurrent angina and reintervention over many years after PTCA, and to similar long-term healthcare costs.

Proceedings ArticleDOI
04 Jan 1998
TL;DR: Four different methods for selecting thresholds that work on very different principles of either the noise or the signal is modelled and the model covers either the spatial or intensity distribution characteristics.
Abstract: Image differencing is used for many applications involving change detection. Although it is usually followed by a thresholding operation to isolate regions of change there are few methods available in the literature specific to (and appropriate for) change detection. We describe four different methods for selecting thresholds that work on very different principles. Either the noise or the signal is modelled, and the model covers either the spatial or intensity distribution characteristics. The methods are: 1) a Normal model is used for the noise intensity distribution, 2) signal intensities are tested by making local intensity distribution comparisons' in the two image frames (i.e. the difference map is not used), 3) the spatial properties of the noise are modelled by a Poisson distribution, and 4) the spatial properties of the signal are modelled as a stable number of regions (or stable Euler number).

Journal ArticleDOI
TL;DR: The findings suggest that design and engineering is constructed through the interactions of multiple actors, and that artefacts and representations of the design process have a key function in the organisation of this work.

Journal ArticleDOI
TL;DR: This paper showed that noise trading is an important contributor to asymmetric effects in the response of volatility to news, and that futures trading improves market dynamics in processing news by transferring noise trading from spot to futures markets.
Abstract: The asymmetric response of volatility to news has been attributed to leverage effects, but the authors show that noise trading is an important contributor to asymmetric effects. Contrary to the traditional view, introducing futures trading has no detrimental impact on the underlying markets. Futures trading improves market dynamics in processing news by transferring noise trading from spot to futures markets.

Journal ArticleDOI
TL;DR: The authors apply a test where the null hypothesis is violated only when all series are stationary, and reject non-stationarity for real dollar rates for real exchange rate series with respect to a single series.

Journal ArticleDOI
TL;DR: In this paper, the authors suggest that a concurrent engineering approach in construction may significantly improve the way in which projects are procured, and propose a simple model demonstrating how concurrent engineering can contribute to project effectiveness.

Proceedings ArticleDOI
03 Jul 1998
TL;DR: In this paper, a formal characterisation is provided which not only clearly distinguishes persuasion from negotiation, but also introduces three other dialogue types, and sets all five in a coherent framework.
Abstract: Sophisticated models of inter-agent communication are making increasing use of intuitive notions of persuasion and negotiation. In this paper, a formal characterisation is provided which not only clearly distinguishes persuasion from negotiation, but also introduces three other dialogue types, and sets all five in a coherent framework. The notion of a dialogue frame is introduced, and is used to explore the dialogue typology and one of its important features, the concept of functional embedding. The approach offers a number of substantial benefits, including (i) the provision of definitions for classes of communicative encounters, (ii) improvements in expressive capability, (iii) facilitating comparison between diverse multi-agent research, and in some cases, (iv) reducing computational cost.

Book
01 Jun 1998
TL;DR: In this paper, the effects of scandium on aluminum alloys from a physico-chemical viewpoint are studied, and the authors present binary, ternary, and more complex phase diagrams for these alloys and consider in detail recrystallization, superplastic behavior, and decomposition of supersaturated solid solutions.
Abstract: This is the first book to generalize and analyze the extensive experimental and theoretical results on the phase composition, structure, and properties of aluminum alloys containing scandium. The effects of scandium on these properties are studied from a physico- chemical viewpoint. The authors present binary, ternary, and more complex phase diagrams for these alloys and consider in detail recrystallization, superplastic behavior, and decomposition of supersaturated solid solutions and the effects of solidification conditions on phase equilibria.

Journal ArticleDOI
TL;DR: The occurrence of early ovo-testes in some fish with completely regressed testes suggests that oogenesis may proceed in testes which have first been inhibited (demasculinised) following estrogenic stimulus.

Journal ArticleDOI
TL;DR: Exposure of natural populations of fish to these chemicals at concentrations currently measurable in the aquatic environment may have an impact on the performance of those populations, and an appropriate OSI is a crucial factor in successful reproduction.
Abstract: The alkylphenol ethoxylates (APEOs) are a major group of non-ionic surfactants. Biodegradation of these compounds is incomplete during sewage treatment, thus they are ubiquitous aquatic pollutants. All the main degradation products of APEOs have recently been demonstrated to have estrogenic properties in vitro, but their effects in vivo remain to be established. In this study, female juvenile rainbow trout (Oncorhynchus mykiss Walbaum) were exposed to octylphenol (OP), nonylphenol (NP), nonylphenol diethoxylate (NP2EO) and nonylphenol mono-carboxylic acid (NP1EC) at environmentally relevant concentrations (Experiment 1: 1, 10 and 50 ug/L; Experiment 2: 1, 10 and 30 ug/L). Exposure to APEO’s commenced at hatch (day 0) and was terminated on day 22 (Expt. 1) or day 35 (Expt. 2). Body weight and fork length of representative samples of fish from each treatment group were recorded at intervals up to 108 days (Expt. 1) or 466 days (Expt. 2). In Experiment 1, significant differences in size of the exposed fish, related to treatment, were still apparent on day 108, 86 days after withdrawal of the treatments. These observations were confirmed during Experiment 2, in which significant changes in body weight and fork length as a consequence of exposure to the compounds were observed approximately 15 days after exposure was terminated. These differences were sustained for at least 466 days in the case of NP and NP1EC. In addition, the ovosomatic index (OSI) of fish exposed to NP and NP1EC was significantly affected by the treatment. Survival of fish in the natural environment is strongly influenced by body size, and an appropriate OSI is a crucial factor in successful reproduction. Therefore, exposure of natural populations of fish to these chemicals at concentrations currently measurable in the aquatic environment may have an impact on the performance of those populations.

Journal ArticleDOI
TL;DR: The results suggest that the diagnostic and therapeutic 'impacts' of MRI were valued by many respondents and have highlighted a number of important issues for the design and analysis of future health-related conjoint studies, including the use of treatment cost as an attribute, dealing with data from lexicographic respondents, and distinguishing between points of indifference and missing data.
Abstract: The conventional approach to the diagnosis and treatment of severe knee injuries is arthroscopy, a minimally invasive surgical procedure. Since arthroscopy is an invasive technique that carries risks, magnetic resonance imaging (MRI) is increasingly being used for diagnosis. MRI is potentially associated with diagnostic and therapeutic ‘impacts’, in that arthroscopy can be avoided. This paper reports a discrete choice conjoint analysis exercise that assessed the value placed on such ‘impacts’ by potential patients and investigated the degree to which respondents were willing to trade between process and outcome. The marginal rates of substitution between attributes were estimated. The results suggest that the diagnostic and therapeutic ‘impacts’ of MRI were valued by many respondents. The study has highlighted a number of important issues for the design and analysis of future health-related conjoint studies, including the use of treatment cost as an attribute, dealing with data from lexicographic respondents, and distinguishing between points of indifference and missing data. © 1998 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this article, the authors review and discuss the current status of the applications of these optical techniques for in-cylinder mixture formation studies and provide appropriate references to the technical literature, which will be of further assistance to readers interested in particular application of each technique.

Journal ArticleDOI
TL;DR: The research culture of practising nurses, health visitors and midwives, and their managers is described by describing the nature of research, its role, and the opportunities and constraints which effect its dissemination and utilization.
Abstract: To ensure effective utilization of research in nursing more evidence is needed which illuminates the way nurses think about research, the value which they put on it, and how they envisage that it may help or hinder them in their everyday work. This English study aimed to meet these objectives by describing the research culture of practising nurses, health visitors and midwives, and their managers. It rests on two assumptions. Firstly that the reasons why practitioners do, or do not, base their practice on research are complex, and secondly, that interventions to increase research utilization must be grounded in an appreciation of this complex ‘whole’. Thus the study took a qualitative approach to exploring: what participants thought and felt about research; the current status of research based practice; and the opportunities and constraints to increasing research based practice. The results confirm the hypothesis that many factors, both individual and organizational affect research utilization. Furthermore, practitioners and managers hold differing perceptions regarding the nature of research, its role, and the opportunities and constraints which effect its dissemination and utilization. The implications of the results for education, policy and practice are discussed.

Journal ArticleDOI
TL;DR: In this article, a group of small companies that were retailing on the Web were surveyed three times over this period, collecting both quantitative and qualitative data and visible data from their Web sites.
Abstract: From July 1995 until July 1996 we followed a group of small companies that were retailing on the Web. We surveyed our sample three times over this period, collecting both quantitative and qualitative data and visible data from their Web sites. Our intention was to initiate research into successful Web‐based retail ‐ put simply, what makes a small company successful on the Web? Using ideas from grounded theory and our findings, we suggest important factors and constructs that can be used for further work in this area.

Journal ArticleDOI
TL;DR: In this paper, a review of the existing literature on computer-aided process planning (CAPP) has been made with the objective of gaining insights into the design and implementation of CAPP systems.
Abstract: During the last decade, computer-aided process planning (CAPP) has received much attention both from researchers and practitioners. One of the reasons for this is the role of CAPP in reducing throughput time and improving quality. An attempt has been made in this paper to review the existing literature with the objective of gaining insights into the design and implementation of CAPP systems. The literature available (1989–1996) on CAPP has been reviewed based on the types of systems. The advantages and disadvantages of such systems are presented. Finally, future research directions are indicated.

Journal ArticleDOI
01 Jan 1998
TL;DR: In this paper, the effects of carbon dioxide (CO₂), a principal constituent of EGR, on combustion and emissions were analyzed and quantified experimentally on a high-speed direct injection diesel engine.
Abstract: The investigation was conducted on a high-speed direct injection diesel engine and was concerned with the effects of exhaust gas recirculation (EGR) on diesel engine combustion and emissions. In particular, the effects of carbon dioxide(CO₂), a principal constituent of EGR, on combustion and emissions were analysed and quantified experimentally. The use of CO₂ to displace oxygen(O₂) in the inlet air resulted in reduction in the O₂ supplied to the engine(dilution effect), increased inlet charge thermal capacity(thermal effect), and, potentially, participation of the CO₂ in the combustion process (chemical effect). In a separate series of tests the temperature of the engine inlet charge was raised gradually in order to simulate the effect of mixing hot EGR with engine inlet air. Finally, tests were carried out during which the CO₂ added to the engine air flow increased the charge mass flowrate to the engine, rather than displacing some of the O₂ in the inlet air. It was found that when CO₂ displaced O₂ in the inlet charge, both the chemical and thermal effects on exhaust emissions were small. However, the dilution effect was substantial, and resulted in very large reductions in exhaust oxides of nitrogen (NO_x) at the expense of higher particulate and unburned hydrocarbon (uHC) emissions. Higher inlet charge temperature increased exhaust NO_x and particulate emissions, but reduced uHC emissions. Finally, when CO₂ was additional to the inlet air charge(rather than displacing O₂), large reductions in NO_x were recorded with little increase in particulate emissions.

Journal ArticleDOI
TL;DR: This paper provided a historical review and empirical investigation of the availability and the effectiveness of different types of mediator in associative learning, as inferred from subjects' retrospective reports, and argued that retrospective mediator reports provide valid accounts of the cognitive processes that occur at the time of learning and that play a causal role in determining the subsequent level of retention.
Abstract: This paper provides a historical review and empirical investigation of the availability and the effectiveness of different types of mediator in associative learning, as inferred from subjects’ retrospective reports. Mental imagery is a preferred mediational strategy in the learning of pairs of common concrete nouns, and its use is associated with a high level of recall performance. Its availability and its effectiveness are both enhanced if subjects are given interactive imagery instructions. It is argued that retrospective mediator reports provide valid accounts of the cognitive processes that occur at the time of learning and that play a causal role in determining the subsequent level of retention.

Proceedings ArticleDOI
01 Dec 1998
TL;DR: The usability of simulation modelling for evaluating alternative business process strategies is investigated and the case for a wider use of simulation techniques by the business community is supported.
Abstract: Globalisation and competitive pressure urge many organisations to radically change business processes. Although this approach can provide significant benefits such as reducing costs or improving efficiency, there are substantial risks associated with it. Using simulation for modelling and analysis of business processes can reduce that risk and increase the chance for success of business process re-engineering projects. This paper investigates the potential of simulation modelling to be used for modelling business processes and supports the case for a wider use of simulation techniques by the business community. Following a discussion on business process modelling methods and tools, the usability of simulation modelling for evaluating alternative business process strategies is investigated. Examples of simulation models representing business processes are presented and discussed.

Proceedings ArticleDOI
23 Feb 1998
TL;DR: In this paper, the effects of exhaust gas recirculation on diesel engine exhaust emissions were isolated and studied in earlier investigations (1,2,3,4,5,6).
Abstract: The effects of Exhaust Gas Recirculation (EGR) on diesel engine exhaust emissions were isolated and studied in earlier investigations (1,2,3,4,5). This paper analyses the heat release patterns during the combustion process and co-relates the results with the exhaust emissions. The EGR effects considered include the dilution of the inlet charge with CO2 or water vapour, the increase in the inlet charge temperature, and the thermal throttling arising from the use of hot EGR. The use of diluents (CO2 and H 2O), which are the principal constituents of EGR, caused an increase in ignition delay and a shift in the location of start of combustion. As a consequence of this shift, the whole combustion process was also shifted further towards the expansion stroke. This resulted in the products of combustion spending shorter periods at high temperatures which lowered the NOx formation rate. In addition, the longer ignition delay period provided more time for the fuel top penetrate which could have led to larger amounts of gases in the flame envelop, thereby lowering the combustion temperature and resulting in lower NOx formation. Although the increased ignition delay period is expected to cause increasing amount of fuel being burned during the pre-mixed burning period, however, the reduction in oxygen availability associated with the application of EGR diluents reduced the rate at which the fuel burnt in the pre-mixed phase. Moreover, the shift of the combustion process towards the expansion stroke resulted in earlier quenching of the combustion process, that is, shorter combustion duration, which yielded higher levels of products of incomplete combustion in the exhaust. The different effects of inlet charge thermal throttling (associated with the use of hot EGR) were simulated and the heat release patterns were analysed. The reduction in the inlet charge oxygen, resulting from throttling the inlet charge, caused an increase in the ignition delay; however, this increase was largely offset by reductions in ignition delay due to increased inlet charge temperature and decreased inlet charge mass. Copyright © 1998 Society of Automotive Engineers, Inc.