Showing papers by "Brunel University London published in 1994"

Estrogenic Effects of Effluents from Sewage Treatment Works

Abstract: The occurrence of hermaphrodite fish in the lagoons of sewage treatment works led us to hypothesize that sewage effluent might contain a substance, or substances, estrogenic to fish. to test this hypothesis, we placed cages containing rainbow trout in the effluent from sewage-treatment works, and one to three weeks later measured the vitellogenin concentration in the plasma of the fish. Vitellogenin is a protein synthesized by the liver of oviparous fish in response to estradiol stimulation; it is then conveyed by the blood to the ovary, where it is sequestered by oocytes to form the yolk. Thus, the presence of vitellogenin in the plasma is indicative of estrogenic stimulation of the liver. an initial study, at a sewage-treatment works, showed that plasma vitellogenin concentrations rose rapidly and very markedly (over 1000-fold in three weeks) when trout were maintained in the effluent. an extensive nationwide survey was then conducted. Results were obtained from fifteen sewage-treatment works d...

Scientific practice and ordinary action : ethnomethodology and social studies of science

Abstract: Introduction 1. Ethnomethodology 2. The demise of the 'old' sociology of science 3. The rise of the new sociology of scientific knowledge 4. Phenomenology and protoethnomethodology 5. Wittgenstein, rules, and epistemology's topic 6. Molecular sociology 7. From quiddity to haecceity: ethnomethodological studies of work Conclusion.

Uncertainty in the economic evaluation of health care technologies: The role of sensitivity analysis

Abstract: Given the increased use of economic evaluation to inform decision making in the health service, it is particularly important that the research methods used are critically assessed and, where possible, improved. The systematic handling of uncertainty in economic evaluation is an important area that remains methodologically underdeveloped. With the increased use of the clinical trial as a vehicle for economic evaluation, there has been recent interest in how the statistical methods routinely employed to handle uncertainty in clinical research might be applied to economic evaluation. This paper reviews the types of uncertainty that exist in economic evaluation and argues that some forms of uncertainty are not amenable to statistical methods. Sensitivity analysis is not a single approach but can take a number of different forms. The different types of sensitivity analysis are reviewed, with an indication of their strengths and weaknesses in relation to the different types of uncertainty in economic evaluation.

Increased levels of lipid hydroperoxides in the parkinsonian substantia nigra: An HPLC and ESR study

Abstract: Previous studies examining the involvement of oxidative stress in the substantia nigra in Parkinson's disease have measured terminal products of lipid peroxidation or the function of antioxidant defense systems. We report a more specific early marker of lipid peroxidation, lipid hydroperoxides, in a high-performance liquid chromatography (HPLC) and electron spin resonance (ESR) investigation. HPLC-chemiluminescent detection revealed two classes of lipid hydroperoxides in brain tissue extracts--free fatty acid hydroperoxides and cholesterol lipid hydroperoxides. Only cholesterol lipid hydroperoxides were consistently detected in all tissue extracts. Cholesterol lipid hydroperoxides had a 10-fold increase in the Parkinson's disease substantia nigra compared to control subjects. ESR detection of radical degradation products, including those of lipid hydroperoxides, in nigral homogenates incubated with the spin trap N-t-butyl-alpha-phenyl nitrone (PBN) showed a marked variation in ESR signal between tissues. Despite the increased levels of lipid hydroperoxides in parkinsonian substantia nigra, there was no overall difference in ESR signal intensity between nigral tissues from controls and from patients with Parkinson's disease. The increased levels of an early component of the peroxidation chain in substantia nigra in Parkinson's disease support the hypothesis of a continuous toxic process involving oxygen radical activity. However, using previously frozen tissue, ESR evidence for increased radical formation could not be demonstrated.

Mature students in higher education: I. A literature survey on approaches to studying

Abstract: Although mature students are often said to be deficient in study skills, most research into approaches to studying in higher education has ignored age as an important explanatory variable. There is nevertheless a consistent suggestion in research using inventories and questionnaires on study processes that mature students exhibit more desirable approaches to academic learning. In particular, mature students seem to be more likely than younger students to adopt a deep approach or a meaning orientation, and conversely they seem to be less likely to adopt a surface approach or a reproducing orientation towards their academic work. Three explanations for this are: that mature students are more motivated by intrinsic goals; that younger students acquire a surface approach to learning in the final years of secondary education; and that the prior life experience of mature students promotes a deep approach towards studying in higher education.

Cultural Specificity of Approaches to Studying in Higher Education: A Literature Survey.

Abstract: Students in higher education exhibit different approaches to learning, but there is evidence that these vary systematically from one culture to another. The broad distinction between an orientation towards comprehending the meaning of learning materials and an orientation towards merely reproducing those materials seems to be a universal feature of all systems of higher education. The former is both consistent and coherent, apparently reflecting the relatively high degree of agreement that exists across different cultures with regard to the goals and purposes of higher education. The latter reflects students' attempts to cope with academic practices that are inappropriate to those goals and purposes; it is more fragmented and more likely to be constructed in a way that is distinctive to each particular cultural context.

An assessment of expressions for the apparent thermal conductivity of cellular materials

Abstract: Diverse expressions for the thermal conductivity of cellular materials are reviewed. Most expressions address only the conductive contribution to heat transfer; some expressions also consider the radiative contribution. Convection is considered to be negligible for cell diameters less than 4 mm. The predicted results are compared with measured conductivities for materials ranging from fine-pore foams to coarse packaging materials. The dependencies of the predicted conductivities on the material parameters which are most open to intervention are presented graphically for the various models.

Beyond the qualitative paradigm: A framework for introducing diversity within qualitative psychology

Abstract: The case for qualitative research in psychology is considered. We argue against the idea that qualitative research is merely a matter of technique or method, and question the utility of viewing it as a unitary paradigm. Rather, the links between epistemology, methodology, and method are explored within three theorized strands of qualitative inquiry, making reference to illustrative projects. Each strand is organized around a different approach to the issues of justifying and warranting psychological knowledge: (1) reliability and validity; (2) generativity and grounding; and (3) discourse and reflexivity. These are exemplified in Miles and Huberman's ‘data display’ model, Glaser and Strauss' method of ‘grounded theory’, and in various forms of ‘discourse’ analysis. Reflections upon points of contact between the three strands address two main issues: (1) rendering research publicly accountable; and (2) challenging relativism.

Gender differences in mental rotation

Abstract: Two experiments were carried out to compare the performance of male and female students at different educational levels on tasks that required mental rotation. Exp. 1 also compared their performance on an overt, male-typed version and a disguised, female-typed version of the same task. Amongst introductory undergraduate students, men performed significantly better than women, but this difference was as pronounced on the disguised, female-typed version as on the overt, male-typed task. However, there was no sign of any gender difference on the overt task in advanced undergraduate and postgraduate students. The latter finding was not replicated in Exp. 2, in which significant effects of gender regardless of the students' educational level were noted. Nevertheless, the effect size was significantly smaller than that obtained for comparable students tested on the same task during the 1970s. Taken together, these results confirm that gender differences in at least some aspects of mental rotation may be abolished by educational experience and that gender differences in mental rotation have become smaller over the last 20 years. Such findings favor sociocultural explanations of gender differences in mental rotation rather than biological explanations.

Mature Students in Higher Education: Academic Performance and Intellectual Ability.

Abstract: Mature students are sometimes said to be deficient in the basic skills needed for effective studying in higher education or to be impaired by age-related intellectual deficits. However, the research literature on the academic performance of mature students contains no good evidence that mature students perform any less well than younger students on courses of study in higher education. Moreover, the idea that normal ageing impairs the capacity for learning in higher education is most questionable: even the oldest mature students can obtain good results when assessed by means of both examinations and coursework.

The application of magnesium hydroxide as a fire retardant and smoke-suppressing additive for polymers

Abstract: The use of magnesium hydroxide as a fire-retardant additive in polymers is discussed in terms of its particle characteristics, thermal properties and factors influencing the mechanism of action. Consideration is also given to its role in reducing smoke evolution during polymer combustion.

Optimized pump scheduling in water distribution systems

Abstract: A method based on nonlinear programming for determining the optimal operation of general water distribution systems containing multiple sources and reservoirs is presented. The problem is formulated and solved so that, given the forecasted demands for the coming 24 hours, the initial and final conditions in the reservoirs, the unit and maximum demand electricity charge, and the constraints in the hydraulic properties of all system components, an optimized pumping schedule is found. An optimization algorithm which employs the generalized reduced gradient method and the nonlinear sensitivity analysis has been developed for a basic scheduling problem in which only unit charges are considered. The maximum demand charge, which is weighted by varying degrees from day to day, is incorporated into the scheduling problem. The algorithm uses a feasible initial solution as the starting solution and iterates so that all the interim solutions are feasible.

Is the gilt-equity yield ratio useful for predicting UK stock returns?

Abstract: The ratio of a long government bond yield to the equity market dividend yield, the Gilt-Equity Yield Ratio (GEYR), is commonly used by analysts in the UK as a means of determining the cheapness of equity investment relative to investment in gilts. Analysts use the ratio to predict future movements in equity prices using buy/sell thresholds, implicitly assuming that there is a long-run arbitrage relation between the equity market and the government bond market. A formal econometric analysis confirms that the GEYR is indeed a useful predictor of equity returns in the UK.

Prediction of mobile radio wave propagation over buildings of irregular heights and spacings

Abstract: Two models of mobile radio wave propagation over buildings are presented. The first, the flat edge model, provides a simple yet accurate representation when buildings are assumed to be of constant height and spacing. The second model combines the first with a rapid new method of calculating multiple edge diffraction to allow deterministic predictions with arbitrary buildings and spacings. This allows predictions to be made with real building data, and the effect of building variations on location variability of the received signal to be assessed. Both models are compared with measurements made in suburban areas in the 900 and 1800 MHz bands and excellent agreement is obtained. >

The welfare problems of laying hens in battery cages

Abstract: So far as feeding, health and protection from cannibalism are concerned, the welfare needs of laying hens can be well catered for in cages. In other respects, however, cages fail to provide for hens' welfare needs. Deprived of litter, caged hens are prevented from dust bathing and foraging. Without access to a nest site, nesting motivation is frustrated and without a perch, roosting is prevented. Restrictions on movement within a cage cause frustration and prevent normal bone maintenance, particularly in the legs and wings. Confinement in a battery cage is concluded to cause suffering to laying hens in several different ways.

Measurement of the production rates of charged hadrons in e+ e- annihilation at the Z0

Abstract: The inclusive production rates of π±,K± andp\(\bar p\) inZ0 decays have been measured with the OPAL detector at LEP. Using the energy loss measurement in the jet chamber, the momentum range up to the beam energy (45.6 GeV/c) has been covered. Differential cross sections and total particle yields are given. Comparisons of the inclusive momentum spectra and the total rates with predictions of the JETSET and the HERWIG Monte Carlo model are presented. The total single rates are found to be 17.05±0.43 π±, 2.42±0.13K± and 0.92±0.11p\(\bar p\) per hadronic event. Predictions of JETSET for cross sections and total rates agree very well for π±; however, for momenta greater than 4 GeV/c,K± rates are underestimated and\(\bar p\) rates are overestimated. Combined with data of other particle species there is evidence that the peak positions in the ξ=ln(1/x p ) distributions show a different mass dependence for mesons and baryons. However, both JETSET and HERWIG Monte Carlo predictions agree with the observed data.

Precise Measurement of the Left-Right Cross Section Asymmetry in Z Boson Production by e+e- Collisions

Abstract: We present a precise measurement of the left-right cross section asymmetry ([ital A][sub [ital L][ital R]]) for [ital Z] boson production by [ital e][sup +][ital e][sup [minus]] collisions. The measurement was performed at a center-of-mass energy of 91.26 GeV with the SLD detector at the SLAC Linear Collider (SLC). The luminosity-weighted average polarization of the SLC electron beam was (63.0[plus minus]1.1)%. Using a sample of 49 392 [ital Z] decays, we measure [ital A][sub [ital L][ital R]] to be 0.1628[plus minus]0.0071(stat)[plus minus]0.0028(syst) which determines the effective weak mixing angle to be sin[sup 2][theta][sub [ital W]][sup eff]=0.2292[plus minus]0.0009(stat) [plus minus]0.0004(syst).

The time trade-off technique: how do the valuations of breast cancer patients compare to those of other groups?

Abstract: The time trade-off method was incorporated into a study of valuation of health states following treatment for breast cancer. A major aim of the work was to determine whether different groups give different valuations. The time trade-off technique was simple and quick to administer, acceptable to subjects, and produced different values in different groups. Age and sex of valuers had some influence: the most striking differences were found between women who had experlenced breast cancer and those who had not. The time trade-off method has considerable potential in health state valuation. The choice of valuers needs to be further explored.

Audit or evaluation? a national audit office vfm study

Abstract: This article presents a case study of an important but relatively neglected aspect of the British policy process - the Value for Money (VIM) studies undertaken by the National Audit Office. It analyses in detail the conduct of one particular study, including the reactions of the audited bodies and the parliamentary activity which followed the publication of the NAO report. The case is then used to illuminate what appear to be some more general characteristics of the NAO's approach. It is concluded that NAO VFM work marks an important step beyond traditional audit for regularity and/or economy, and that it significantly enhances democratic accountability. Yet at the same time this work falls short of a full-blooded evaluation. Indeed, it appears to take place within quite prominent constraints, some of which were built into the legislation setting up the NAO but others of which could conceivably be eased, even without new statutory authority.

QCD studies using a cone-based jet finding algorithm for e + e − collisons at LEP

Abstract: We describe a cone-based jet finding algorithm (similar to that used in $$\bar p$$ p experiments), which we have applied to hadronic events recorded using the OPAL detector at LEP. Comparisons are made between jets defined with the cone algorithm and jets found by the “JADE” and “Durham” jet finders usually used ine + e − experiments. Measured jet rates, as a function of the cone size and as a function of the minimum jet energy, have been compared with O(α 2 ) calculations, from which two complementary measurements $$\alpha _s \left( {M_{Z^0 } } \right)$$ have been made. The results are $$\alpha _s \left( {M_{Z^0 } } \right)$$ =0.116±0.008 and $$\alpha _s \left( {M_{Z^0 } } \right)$$ =0.119±0.008 respectively, where the errors include both experimental and theoretical uncertainties. Measurements are presented of the energy flow inside jets defined using the cone algorithm, and compared with equivalent data from $$\bar p$$ p interactions, reported by the CDF collaboration. We find that the jets ine + e − are significantly narrower than those observed in $$\bar p$$ p. The main contribution to this effect appears to arise from differences between quark- and gluon-induced jets.

A die pressing test for the estimation of agglomerate strength

Abstract: A die pressing test was developed for quick and inexpensive estimation of the agglomerate strength of ceramic powders. The critical nominal pressure (pc) at which contact areas between agglomerates start to increase rapidly was found from the relationship between change in sample height and applied pressure in uniaxial single-ended die pressing. A quantitative microscopic method was used for measuring the area fraction (Ψ) of agglomerates which transmits the force through the assembly. A die pressing agglomerate strength, σd, is defined as σd= 0.7 pc/Ψ. This strength was compared with the agglomerate tensile strength obtained from single agglomerate diametral compression tests and found to be 50% higher than the latter because of multipoint loading. A suggested guideline is that the mean agglomerate tensile strength is approximately 52% of pc determined in a die pressing test for spherical agglomerates. In addition to agglomerate tensile strength, the mean agglomerate size, the interior macropore structure of agglomerates, as well as the packing efficiencies between and inside agglomerates can be estimated by the procedure.

Numerical methods for eighth-, tenth- and twelfth-order eigenvalue problems arising in thermal instability

Abstract: Second-order finite-difference methods are developed for the numerical solutions of the eighth-, tenth- and twelfth-order eigenvalue problems arising in the study of the effect of rotation on a horizontal layer of fluid heated from below. Instability setting-in as overstability may be modelled by an eighth-order ordinary differential equation. When a uniform magnetic field also acts across the fluid in the same direction as gravity, instability setting-in as ordinary convection may be modelled by a tenth-order differential equation, while instability setting-in as overstability may be modelled by a twelfth-order differential equation. The numerical methods are developed by making direct replacements of the derivatives in the differential equations and then by computing the eigenvalues, which may incorporate Rayleigh number, horizontal wave speed and a time constant, from the resulting algebraic eigenvalue problem. The eigenvalues are also computed by writing the differential equations as systems of second-order differential equations and then using second- and fourth-order methods to obtain the eigenvalues. Numerical results obtained using the two approaches are compared with estimates appearing in the literature.