Showing papers by "University of Exeter published in 2004"

Mangroves enhance the biomass of coral reef fish communities in the Caribbean.

Abstract: Mangrove forests are one of the world's most threatened tropical ecosystems with global loss exceeding 35% (ref 1) Juvenile coral reef fish often inhabit mangroves, but the importance of these nurseries to reef fish population dynamics has not been quantified Indeed, mangroves might be expected to have negligible influence on reef fish communities: juvenile fish can inhabit alternative habitats and fish populations may be regulated by other limiting factors such as larval supply or fishing Here we show that mangroves are unexpectedly important, serving as an intermediate nursery habitat that may increase the survivorship of young fish Mangroves in the Caribbean strongly influence the community structure of fish on neighbouring coral reefs In addition, the biomass of several commercially important species is more than doubled when adult habitat is connected to mangroves The largest herbivorous fish in the Atlantic, Scarus guacamaia, has a functional dependency on mangroves and has suffered local extinction after mangrove removal Current rates of mangrove deforestation are likely to have severe deleterious consequences for the ecosystem function, fisheries productivity and resilience of reefs Conservation efforts should protect connected corridors of mangroves, seagrass beds and coral reefs

Activating Mutations in the Gene Encoding the ATP-Sensitive Potassium-Channel Subunit Kir6.2 and Permanent Neonatal Diabetes

Abstract: Background Patients with permanent neonatal diabetes usually present within the first three months of life and require insulin treatment. In most, the cause is unknown. Because ATP-sensitive potassium (KATP) channels mediate glucose-stimulated insulin secretion from the pancreatic beta cells, we hypothesized that activating mutations in the gene encoding the Kir6.2 subunit of this channel (KCNJ11) cause neonatal diabetes. Methods We sequenced the KCNJ11 gene in 29 patients with permanent neonatal diabetes. The insulin secretory response to intravenous glucagon, glucose, and the sulfonylurea tolbutamide was assessed in patients who had mutations in the gene. Results Six novel, heterozygous missense mutations were identified in 10 of the 29 patients. In two patients the diabetes was familial, and in eight it arose from a spontaneous mutation. Their neonatal diabetes was characterized by ketoacidosis or marked hyperglycemia and was treated with insulin. Patients did not secrete insulin in response to glucose...

Physisorption Hysteresis Loops and the Characterization of Nanoporous Materials

Abstract: The classification of adsorption hysteresis loops recommended by the IUPAC in 1984 was based on experimental observations and the application of classical principles of pore filling (notably the use of the Kelvin equation for mesopore analysis). Recent molecular simulation and density functional (DFT) studies of the physisorption of gases by model pore structures have greatly improved our understanding of the mechanisms of hysteresis and it is therefore timely to revisit the IUPAC recommendations. In this review, we conclude that there is no immediate need to change the IUPAC classification of physisorption isotherms and hysteresis loops. However, in the light of recent advances, we are able to offer a revised checklist for the analysis of nitrogen isotherms on nanoporous solids: this includes a carefully regulated application of DFT in place of a classical procedure such as the well-known Barrett-Joyner-Halenda (BJH) method.

Motivating Individuals and Groups at Work: A Social Identity Perspective on Leadership and Group Performance

Abstract: We argue that additional understanding of work motivation can be gained by incorporating current insights concerning self-categorization and social identity processes and by examining the way in which these processes influence the motivation and behavior of individuals and groups at work. This theoretical perspective that focuses on the conditions determining different self-definitions allows us to show how individual and group processes interact to determine work motivation. To illustrate the added value of this approach, we develop some specific propositions concerning motivational processes underpinning leadership and group performance.

Surface Plasmon Polaritons and Their Role in the Enhanced Transmission of Light through Periodic Arrays of Subwavelength Holes in a Metal Film

Abstract: We present results of the transmitted, reflected, and absorbed power associated with the enhanced transmittance of light through a silver film pierced by a periodic array of subwavelength holes. Comparing experimentally acquired dispersion curves under different polarization conditions shows that the transmission features of the array are consistent with p-polarized resonant modes of the structure. By exploring the regime in which no propagating diffracted orders are allowed, we further show that the transmittance maxima are associated with both reflectance minima and absorption maxima. These new results provide strong experimental evidence for transmission based on diffraction, assisted by the enhanced fields associated with surface plasmon polaritons.

Aggregation behavior of aqueous solutions of ionic liquids

Abstract: The aggregation behavior in aqueous solutions of three ionic liquids based on the 1-alkyl-3-methylimidazolium cation has been investigated by means of surface tension, conductivity, and small-angle neutron scattering (SANS) measurements. From analysis of the SANS data, models for the shapes and sizes of aggregates have been proposed: the short-chain 1-butyl-3-methylimidazolium tetrafluoroborate [C4mim][BF4] system can be best modeled by treating it as a dispersion of polydisperse spherical aggregates that form above a critical aggregation concentration, whereas the 1-octyl-3-methylimidazolium iodide, [C8mim][I], solutions can be modeled as a system of regularly sized near-spherical charged micelles that form above a critical micelle concentration. Solutions of 1-octyl-3-methylimidazolium chloride, [C8mim][Cl], display weak long-range ordering of possibly disklike particles culminating in the formation of structures with distinct long-range order at higher concentrations.

Physical activity and older adults: a review of health benefits and the effectiveness of interventions

Abstract: The purpose of this multidisciplinary review paper is to critically review evidence from descriptive, efficacy and effectiveness studies concerned with physical activity and older people. Both levels of fitness (aerobic power, strength, flexibility and functional capability) and measures of physical activity involvement decline with age, and the extent to which this is due to a biological ageing processes or disuse (physical inactivity) is critically examined. The review will consider the evidence for a causal relationship between sedentary behaviour/physical activity programmes and cardiovascular, musculoskeletal and psycho-social health, independent living and health-related quality of life into old age. The review also considers the effectiveness of different physical activity interventions for older people and issues relating to cost-effectiveness. The implications for future policy in terms of research, health care services, and education and training are briefly discussed.

Multiobjective Genetic Algorithms for Design of Water Distribution Networks

Abstract: This paper presents a multiobjective genetic algorithm approach to the design of a water distribution network. The objectives considered are minimization of the network cost and maximization of a reliability measure. In this study, a new reliability measure, called network resilience, is introduced. This measure mimics a designer's desire of providing excess head above the minimum allowable head at the nodes and of designing reliable loops with practicable pipe diameters. The proposed method produces a set of Pareto-optimal solutions in the search space of cost and network resilience. Genetic algorithms are observed to be poor in handling constraints. To handle constraints in a better way, a constraint handling technique that does not require a penalty coefficient and is applicable to water distribution systems is presented. The present model is applied to two example problems, which are widely reported. Comparison of the present method with other methods revealed that the network resilience based approach gave better results.

Teaching anatomy without cadavers.

Abstract: Background Anatomy learning is generally seen as essential to medicine, and exposure to cadavers is generally seen as essential to anatomy learning around the world. Few voices dissenting from these propositions can be identified. Aims This paper aims to consider arguments relating to the use of cadavers in anatomy teaching, and to describe the rationale behind the decision of a new UK medical school not to use cadaveric material. Discussion First, the background to use of cadavers in anatomy learning is explored, and some general educational principles are explored. Next, arguments for the use of human cadaveric material are summarised. Then, possible arguments against use of cadavers, including educational principles as well as costs, hazards and practicality, are considered. These are much less well explored in the existing literature. Next, the rationale behind the decision of a new UK medical school not to use cadaveric material is indicated, and the programme of anatomy teaching to be employed in the absence of the use of human remains is described. Curriculum design and development, and evaluation procedures, are briefly described. Issues surrounding pathology training by autopsy, and postgraduate training in surgical anatomy, are not addressed in this paper. Future directions Evidence relating to the effect on medical learning by students not exposed to cadavers is scant, and plainly opportunities will now arise through our programme to gather such evidence. We anticipate that this discussion paper will contribute to an ongoing debate, in which virtually all previous papers on this topic have concluded that use of cadavers is essential to medical learning.

Energy transfer across a metal film mediated by surface plasmon polaritons.

Abstract: Coupled surface plasmon polaritons (SPPs) are shown to provide effective transfer of excitation energy from donor molecules to acceptor molecules on opposite sides of metal films up to 120 nanometers thick. This variant of radiative transfer should allow directional control over the flow of excitation energy with the use of suitably designed metallic nanostructures, with SPPs mediating transfer over length scales of 10–7 to 10–4 meters. In the emerging field of nanophotonics, such a prospect could allow subwavelength-scale manipulation of light and provide an interface to the outside world.

The Individual Within the Group: Balancing the Need to Belong With the Need to Be Different

Abstract: Many theorists have wrestled with the notion of how people balance their need to be included in social groups with their need to be different and distinctive. This question is particularly salient to researchers from the social identity perspective, who have traditionally viewed individual differentiation within groups as being inimical to group identification. In this article we present a number of strategies that people can use to balance their need to belong and their need to be different, without violating social identity principles. First, drawing from optimal distinctiveness theory, we discuss 4 ways in which the need for belonging and the need to be different can be resolved by maximizing group distinctiveness. We then discuss 4 ways in which it is possible to achieve individual differentiation within a group at the same time demonstrating group identification. These strategies are discussed and integrated with reference to recent empirical research and to the social identity perspective.

Massive star formation: nurture, not nature

Abstract: We investigate the physical processes that lead to the formation of massive stars. Using a numerical simulation of the formation of a stellar cluster from a turbulent molecular cloud, we evaluate the relevant contributions of fragmentation and competitive accretion in determining the masses of the more massive stars. We find no correlation between the final mass of a massive star, and the mass of the clump from which it forms. Instead, we find that the bulk of the mass of massive stars comes from subsequent competitive accretion in a clustered environment. In fact, the majority of this mass infalls on to a pre-existing stellar cluster. Furthermore, the mass of the most massive star in a system increases as the system grows in numbers of stars and in total mass. This arises as the infalling gas is accompanied by newly formed stars, resulting in a larger cluster around a more massive star. High-mass stars gain mass as they gain companions, implying a direct causal relationship between the cluster formation process and the formation of higher-mass stars therein.

Intergroup distinctiveness and differentiation: a meta-analytic integration.

Abstract: The authors examined the relation between perceptions of intergroup distinctiveness and intergroup differentiation in a meta-analysis. They tested the social identity theory prediction that low intergroup distinctiveness underlies differentiation (the "reactive distinctiveness" hypothesis) for effects on behavioral and judgmental differentiation. In addition, they examined the moderating power of 4 variables that H. Tajfel and J. C. Turner (1979) predicted would influence differentiation (group identification, relevance of the dimension of comparison, relevance of the outgroup. and nature of intergroup relations). Analysis of 60 tests revealed that the overall effect of distinctiveness on differentiation was not significantly different from 0, but reactive distinctiveness was found on behavioral differentiation measures, whereas reflective distinctiveness was found on judgmental differentiation measures. Only group identification was a reliable moderator. High identifiers showed reactive distinctiveness, whereas low identifiers showed reflective distinctiveness.

Education, Accountability, and the Ethical Demand: Can the Democratic Potential of Accountability Be Regained?

Abstract: This paper analyzes the impact of the idea of accountability on education. It considers the kind of relationships that are promoted or produced by the culture of accountability, both in order to understand what kind of relationships are made possible and to understand what kind of relationships are made difficult, or even impossible, as a result of the accountability regime. The paper explores how the managerial uses of the idea of accountability have become pervasive in contemporary education and how this has changed relationships among students, parents, teachers, and the state. Ultimately, accountability erodes relationships of responsibility. Zygmunt Bauman's “postmodern ethics” is used to gain a detailed understanding of why it has become so much more difficult to develop relationships of responsibility under the accountability regime. Bauman's proposal that we should take responsibility for our responsibility also suggests a starting point from which the democratic potential of accountability might be regained.

Documenting catchment suspended sediment sources: problems, approaches and prospects

Abstract: Establishing catchment suspended sediment sources is fraught with difficulty. Data collection comprises indirect and direct approaches and an overview is provided. The indirect approach uses a range of techniques to measure or evaluate sediment mobilization. Yet, although recent technological advances in surveying, remote sensing and photogrammetry provide improved resolution of temporal and spatial patterns of catchment erosion, these procedures take no account of source - river connectivity and the uncertainties associated with sediment routing. It is therefore only possible to infer the provenance of suspended sediment loads on the exclusive basis of on-site erosion data for different portions of the upstream catchment unless supportive information on sediment delivery is readily available. In contrast, the direct approach attempts to link sediment sources and flux using alternative means and therefore avoids the need for complementary information. Sediment fingerprinting best represents the direct approach to sediment sourcing and there remains substantial scope for exploiting the potential of this technique. The spatial complexity of sediment mobilization and transfer at the catchment scale necessitates a distributed approach to modelling. Recent developments in computer power and programming techniques are proving useful in this respect, but assembling the input and validation data required by distributed models continues to pose problems and it is frequently difficult to apportion the relative contributions from individual sediment sources. General prospects for future developments are discussed.

Operational Optimization of Water Distribution Systems using a Hybrid Genetic Algorithm

Abstract: Genetic algorithm (GA) optimization is well suited for optimizing the operation of water distribution systems, especially large and complex systems. GAs have good initial convergence characteristics, but slow down considerably once the region of optimal solution has been identified. In this study the efficiency of GA operational optimization was improved through a hybrid method which combines the GA method with a hillclimber search strategy. Hillclimber strategies complement GAs by being efficient in finding a local optimum. Two hillclimber strategies, the Hooke and Jeeves and Fibonacci methods, were investigated. The hybrid method proved to be superior to the pure GA in finding a good solution quickly, both when applied to a test problem and to a large existing water distribution system.

Europeanisation: Solution or Problem?

Abstract: Is there something new in recent research on Europeanisation? Or should we go back to what we already know about political integration in Europe and avoid the term? This article reviews recent work in four steps: the identification of the specific domain of Europeanisation; the relationship between Europeanisation, on the one hand, and governance, institutions, and discourse, on the other; the methodological problems and the models emerging in this new field of research; and an assessment of the results arising out of theoretical and empirical research. One theme throughout the article is that, in order to develop a progressive agenda, Europeanisation should be seen as a problem, not as a solution. It is neither a new theory, nor an ad-hoc approach. Rather, it is a way of orchestrating existing concepts and to contribute to cumulative research in political science. Europeanisation does not provide any simple fix to theoretical or empirical problems. Quite the opposite, it can deliver if approached as a set of puzzles. A problem in search of explanation - not the explanation itself (Gualini 2003). The conclusion is that Europeanisation has contributed to the emergence of new insights, original explanations, and interesting questions on three important issues: the understanding and analysis of 'impact', how to endogeneise international governance in models of domestic politics, and the relationship between agency and change. These three issues are prominent in the research agendas of international relations, theoretical policy analysis, and comparative politics. To contribute to major issues at the core of political science is a valuable result for a relatively new field of inquiry.

The star formation rate of the Universe at z~ 6 from the Hubble Ultra-Deep Field

Abstract: We determine the abundance of i′-band dropouts in the recently released HST/ACS Hubble Ultra-Deep Field (UDF). Because the majority of these sources are likely to be z≈ 6 galaxies whose flux decrement between the F775W i′-band and F850LP z′-band arises from Lyman-α absorption, the number of detected candidates provides a valuable upper limit to the unextincted star formation rate at this redshift. We demonstrate that the increased depth of UDF enables us to reach an 8 σ limiting magnitude of z′AB= 28.5 (equivalent to 1.5 h−270 M⊙ yr−1 at z= 6.1, or 0.1 L⋆UV for the z≈ 3U-drop population), permitting us to address earlier ambiguities arising from the unobserved form of the luminosity function. We identify 54 galaxies (and only one star) at z′AB 1.3 over the deepest 11-arcmin2 portion of the UDF. The characteristic luminosity (L⋆) is consistent with values observed at z≈ 3. The faint end slope (α) is less well constrained, but is consistent with only modest evolution. The main change appears to be in the number density (Φ*). Specifically, and regardless of possible contamination from cool stars and lower-redshift sources, the UDF data support our previous result that the star formation rate at z≈ 6 was approximately six times less than at z≈ 3. This declining comoving star formation rate [0.005 h70 M⊙ yr−1 Mpc−3 at z≈ 6 at LUV > 0.1 L⋆ for a Salpeter initial mass function (IMF)] poses an interesting challenge for models which suggest that LUV > 0.1 L⋆ star-forming galaxies at z≃ 6 reionized the Universe. The short-fall in ionizing photons might be alleviated by galaxies fainter than our limit, or a radically different IMF. Alternatively, the bulk of reionization might have occurred at z≫ 6.

Pupils' views on inclusion: moderate learning difficulties and bullying in mainstream and special schools

Abstract: This study examined the views of 101 boys and girls aged 10–11 and 13–14 with statements of special educational needs for moderate learning difficulties. Questions centred on their experiences of school, teaching and learning in mainstream and special schools. The study is set in the context of the international move towards more inclusion of children with disabilities into mainstream schools and the greater importance attached to the child's voice in decision-making in education. Most children expressed positive evaluations of their schools and the teaching they received, while a significant minority expressed mixed views. A significant proportion in the mainstream preferred learning support in withdrawal settings. While the majority in both settings preferred their current school, a significant minority in special school preferred to be in a mainstream setting. A notable emergent theme from the study was the high incidence of ‘bullying’ that was experienced. Though experienced in both settings, those in...

Money and the Early Greek Mind: Homer, Philosophy, Tragedy

Abstract: 1. Introduction Part I. The Genesis of Coined Money: 2. Homeric transactions 3. Sacrifice and distribution 4. Greece and the ancient near East 5. Greek money 6. The preconditions of coinage 7. The earliest coins 8. The features of money Part II. The Making of Metaphysics: 9. Did politics produce philosophy? 10. Anaximander and Xenophanes 11. The many and the one 12. Heraclitus and Parmenides 13. Pythagoreanism and Protagoras 14. Individualisation 15. Appendix: was money used in the early near East?