Semi-parametric modelling of trend in extremes

Assessment of trend has been a topic of major interest in extreme value analysis in recent years. Much of the previous work has focused on using parametric techniques to model trend in extremes. The parametric approach, however, is often not flexible enough for exploratory modelling. In this paper, we discuss and illustrate a semi-parametric method which can be used as an exploratory tool to draw more information about the extremes and to model trend in extremes. Our approach is based on local likelihood fitting of generalized extreme value distribution and related models. It aims to capture the pattern of trend by fitting locally weighted polynomials to the model parameters. We illustrate the application of this methodology in a study investigating changes in extreme temperatures in central England. Bootstrap methods are used to provide a measure of the variability of the fitted quantities

Towards More Accurate Molecular Dynamics Calculation of Thermal Conductivity. Case Study: GaN Bulk Crystals

Significant differences exist among literature for thermal conductivity of various systems computed using molecular dynamics simulation. In some cases, unphysical results, for example, negative thermal conductivity, have been found. Using GaN as an example case and the direct non-equilibrium method, extensive molecular dynamics simulations and Monte Carlo analysis of the results have been carried out to quantify the uncertainty level of the molecular dynamics methods and to identify the conditions that can yield sufficiently accurate calculations of thermal conductivity. We found that the errors of the calculations are mainly due to the statistical thermal fluctuations. Extrapolating results to the limit of an infinite-size system tend to magnify the errors and occasionally lead to unphysical results. The error in bulk estimates can be reduced by performing longer time averages using properly selected systems over a range of sample lengths. If the errors in the conductivity estimates associated with each of the sample lengths are kept below a certain threshold, the likelihood of obtaining unphysical bulk values becomes insignificant. Using a Monte-Carlo approach developed here, we have determined the probability distributions for the bulk thermal conductivities obtained using the direct method. We also have observed a nonlinear effect that can become a source of significant errors. For the extremely accurate results presented here, we predict a [0001] GaN thermal conductivity of 185 $\rm{W/K \cdot m}$ at 300 K, 102 $\rm{W/K \cdot m}$ at 500 K, and 74 $\rm{W/K \cdot m}$ at 800 K. Using the insights obtained in the work, we have achieved a corresponding error level (standard deviation) for the bulk (infinite sample length) GaN thermal conductivity of less than 10 $\rm{W/K \cdot m}$, 5 $\rm{W/K \cdot m}$, and 15 $\rm{W/K \cdot m}$ at 300 K, 500 K, and 800 K respectively

Probability Models for Degree Distributions of Protein Interaction Networks

The degree distribution of many biological and technological networks has been described as a power-law distribution. While the degree distribution does not capture all aspects of a network, it has often been suggested that its functional form contains important clues as to underlying evolutionary processes that have shaped the network. Generally, the functional form for the degree distribution has been determined in an ad-hoc fashion, with clear power-law like behaviour often only extending over a limited range of connectivities. Here we apply formal model selection techniques to decide which probability distribution best describes the degree distributions of protein interaction networks. Contrary to previous studies this well defined approach suggests that the degree distribution of many molecular networks is often better described by distributions other than the popular power-law distribution. This, in turn, suggests that simple, if elegant, models may not necessarily help in the quantitative understanding of complex biological processes.

Momentum relaxation from the fluid/gravity correspondence

We provide a hydrodynamical description of a holographic theory with broken translation invariance. We use the fluid/gravity correspondence to systematically obtain both the constitutive relations for the currents and the Ward identity for momentum relaxation in a derivative expansion. Beyond leading order in the strength of momentum relaxation, our results differ from a model previously proposed by Hartnoll et al. As an application of these techniques we consider charge and heat transport in the boundary theory. We derive the low frequency thermoelectric transport coefficients of the holographic theory from the linearised hydrodynamics.Comment: 19 pages + appendix, v2: references added, typos corrected, v3: version published in JHE

Potential Greenhouse Gas Mitigation from Utilising Pig Manure and Grass for Hydrothermal Carbonisation and Anaerobic Digestion in the UK, EU, and China

Pig manure currently results in sizeable greenhouse gas emissions, during storage and spreading to land. Anaerobic digestion and hydrothermal carbonisation could provide significant greenhouse gas mitigation, as well as generate renewable heat and power (with anaerobic digestion), or a peat-like soil amendment product (with hydrothermal carbonisation). The greenhouse gas mitigation potential associated with avoidance of pig manure storage and spreading in the UK, EU, and China, as well as the potential to provide heat and power by anaerobic digestion and soil amendment products by hydrothermal carbonisation was herein determined. In each case, the mono-conversion of pig manure is compared to co-conversion with a 50:50 mixture of pig manure with grass. Anaerobic digestion displayed a greater greenhouse gas mitigation potential than hydrothermal carbonisation in all cases, and co-processing with grass greatly enhances greenhouse gas mitigation potential. China has the largest greenhouse gas mitigation potential (129 MT CO₂ eq), and greatest mitigation per kg of pig manure (1.8 kgCO₂/kg pig manure volatile solids). The energy grid carbon intensity has a significant impact on the greenhouse gas mitigation potential of the different approaches in the different regions. Pig manure is generated in large amounts in China, and the energy generated from biogas offsets a higher carbon intensity grid. Greenhouse gas savings from the anaerobic digestion of pig manure and grass have been calculated to provide a significant potential for reducing total greenhouse gas emissions representation in China (1.05%), the EU (0.92%), and the UK (0.19%). Overall, the utilisation of pig manure could bring about substantial greenhouse savings, especially through co-digestion of pig manure with grass in countries with large pig farming industries and carbon intense energy mixes

Story in health and social care

This paper offers a brief consideration of how narrative, in the form of people‟s own stories, potentially figures in health and social care provision as part of the impulse towards patient-centred care. The rise of the epistemological legitimacy of patients‟ stories is sketched here. The paper draws upon relevant literature and original writing to consider the ways in which stories can mislead as well as illuminate the process of making individual treatment care plans

Magnetic effects in a holographic Fermi-like liquid

We explore the magnetic properties of the Fermi-like liquid represented by the D3-D7' system. The system exhibits interesting magnetic properties such as ferromagnetism and an anomalous Hall effect, which are due to the Chern-Simons term in the effective gravitational action. We investigate the spectrum of quasi-normal modes in the presence of a magnetic field and show that the magnetic field mitigates the instability towards a striped phase. In addition, we find a critical magnetic field above which the zero sound mode becomes massive.Comment: 18 pages, 15 figure

Prevention is better than cure, but...: Preventive medication as a risk to ordinariness?

Preventive health remains at the forefront of public health concerns; recent initiatives, such as the NHS health check, may lead to recommendations for medication in response to the identification of 'at risk' individuals. Little is known about lay views of preventive medication. This paper uses the case of aspirin as a prophylactic against heart disease to explore views among people invited to screening for a trial investigating the efficacy of such an approach. Qualitative interviews (N=46) and focus groups (N=5, participants 31) revealed dilemmas about preventive medication in the form of clashes between norms: first, in general terms, assumptions about the benefit of prevention were complicated by dislike of medication; second, the individual duty to engage in prevention was complicated by the need not to be over involved with one's own health; third, the potential appeal of this alternative approach to health promotion was complicated by unease about the implications of encouraging irresponsible behaviour among others. Though respondents made different decisions about using the drug, they reported very similar ways of trying to resolve these conflicts, drawing upon concepts of necessity and legitimisation and the special ordinariness of the particular dru