Critical Behaviour of the Two Dimensional Step Model

We use finite--size scaling of Lee--Yang partition function zeroes to study the critical behaviour of the two dimensional step or sgn $O(2)$ model. We present evidence that, like the closely related $XY$--model, this has a phase transition from a disordered high temperature phase to a low temperature massless phase where the model remains critical. The critical parameters (including logarithmic corrections) are compatible with those of the $XY$--model indicating that both models belong to the same universality class.Comment: 6 pages latex, 3 postscript figures, compressed and uuencoded (revised remarks on Lee_Yang theorem, version to appear in Phys Rev B

Modeling Stable Matching Problems with Answer Set Programming

The Stable Marriage Problem (SMP) is a well-known matching problem first introduced and solved by Gale and Shapley (1962). Several variants and extensions to this problem have since been investigated to cover a wider set of applications. Each time a new variant is considered, however, a new algorithm needs to be developed and implemented. As an alternative, in this paper we propose an encoding of the SMP using Answer Set Programming (ASP). Our encoding can easily be extended and adapted to the needs of specific applications. As an illustration we show how stable matchings can be found when individuals may designate unacceptable partners and ties between preferences are allowed. Subsequently, we show how our ASP based encoding naturally allows us to select specific stable matchings which are optimal according to a given criterion. Each time, we can rely on generic and efficient off-the-shelf answer set solvers to find (optimal) stable matchings.Comment: 26 page

The hospitals/residents problem with ties

The hospitals/residents problem is an extensively-studied many-one stable matching problem. Here, we consider the hospitals/residents problem where ties are allowed in the preference lists. In this extended setting, a number of natural definitions for a stable matching arise. We present the first linear-time algorithm for the problem under the strongest of these criteria, so-called super-stability . Our new results have applications to large-scale matching schemes, such as the National Resident Matching Program in the US, and similar schemes elsewhere

The Modernization of Legal Lists

Worldwide, fatal traffic injuries and drowning deaths are important problems. The aim of this thesis was to investigate the cirumstances of fatal and non-fatal traffic injuries and drowning deaths in Sweden including analysis of the presence of alcohol and drugs, which are considered to be major risk factors for these events. Data where obtained from the database of National Board of Forensic Medicine. In the first study, we investigated 420 passenger deaths from 372 crashes during 1993-1996. There were 594 drivers involved. In total, 21% of the drivers at fault were alcohol positive compared to 2% of drivers not at fault (p<0.001) (Paper I). During 2004-2007, crashes involving 56 fatally and 144 non-fatally injured drivers were investigated in a prospective study from Northern Sweden (Paper II). The drivers were alcohol positive in 38% and 21%, respectively. Psychoactive drugs were found in 7% and 13%, respectively. Benzodiazepines, opiates and antidepressants were the most frequent drugs found in drivers. Illict drugs were found 9% and 4% respectively, with tetrahydrocannabinol being the most frequent of these drugs (Paper II). We investigated 5,125 drowning deaths in Sweden during 1992-2009 (Paper III). The incidence decreased on average by about 2% each year (p<0.001). Unintentional drowning was most common (50%). Alcohol was found in 44% of unintentional, 24% of intentional, and 45% of undetermined drowning deaths. Psychoactive substances were detected in 40% and benzodiazepines were the most common substance. Illicit drugs were detected in 10%. Of all drowning deaths, a significantly higher proportion females commited suicide compared with males (55% vs. 21%, p<0.001). Suicidal drowning deaths (n=129) in Northern Sweden were studied further in detail (Paper IV). of these, 53% had been hospitalized due to a psychiatric diagnosis within five years prior to the suicide. Affective and psychotic disorders were the most common psychiatric diagnoses. Almost one third had performed a previous suicide attempt. One fourth had committed suicide after less than one week of discharge from hospital. Alochol was found in 16% and psychoactive drugs in 62% of these cases, respectively.  In conclusion, alcohol and psychoactive drugs are commonly detected among injured drivers and drowning victims, and probably play a role in these events. Most of the individuals that tested positive for alcohol and high blood concentrations, indicating alochol dependence or abuse. This association warrants futher attention when planning future prevention.

Colonial encounters: white, middle-class, British citizens in Late-Colonial India

This research into the Special Collections Archive at Exeter University and India Office Records at the British Library, explores everyday life for white, middle-class British citizens in India between 1914 and 1941. Building on existing scholarship and methodologies outlined by Ann Laura Stoler (1995; 2009), Antoinette Burton (2003) and Homi Bhabha (1984), this project considers the ways late-colonial gender and class identities inform constructions of otherness; exemplified by case studies, vignettes and recollections of homelife and leisure, local communities and professional obligations in India. Drawing on records from the late-colonial period this thesis explores the specific experiences and articulations of three individuals who grew up in Britain, spent decades in India, and later returned to Devon, South West England. The collections are records of the complications of establishing a family, socialising with peers, controlling domestic spaces and employment in India. Through immersion into the archive (Stoler 2009) and close reading of a diverse range of source material, including correspondence, memoir, articles, lecture notes and legal papers, I aim to nuance our understanding of colonial relationships by considering individual narratives. Exploring the memoir of Violet Fulford Williams, and her husband, Henry’s private ‘India Notes’, we see that while their experiences were chronologically similar, the couple had substantially different responsibilities, and engaged in very different negotiations and recollections. In this case, gender, class, memory and narrative style all play a part in articulating their encounters with India. Likewise, through court papers and correspondence we see how one High Court Judge, Sir Leonard Costello, became responsible for ruling on the identity of an Indian Subject, and promoted his own self-interest through retirement and law-making in both the UK and India. At the micro-scale Costello, Violet and Henry display classic colonialist attitudes as well as a sensitivity towards the colony, where they built their homes and careers. I demonstrate how their commentaries and categorisations exemplify the complexity of living in India as members of colonial leadership, mediated through their professional/familial obligations, race, gender and class. Bibliography: Bhabha, Homi. 1984. ‘Of Mimicry and Man: The Ambivalence of Colonial Discourse’, Discipleship: A Special Issue on Psychoanalysis, 28: 125-33, Burton, Antoinette. 2003. Dwelling in the Archive: Women Writing House, Home, and History in Late Colonial India, 1st edn (Oxford: Oxford University Press) Stoler, Ann Laura. 1995. Race and the Education of Desire: Foucault’s History of Sexuality and the Colonial Order of Things, (North Carolina: Duke University Press) -- 2009. Along the Archival Grain: Epistemic Anxieties and Colonial Common Sense, (New Jersey: Princeton University Press

Assessing the potential of heat pumps to reduce energy-related carbon emissions from UK housing in a changing climate

This thesis describes three connected stages of development and analysis of residential heat pump energy use: firstly, the analysis of heat pump performance data from a monitoring study of ground source heat pumps; secondly, the definition and development of a generalised residential heat pump energy model embedded within an enhanced dwelling energy model; finally, the analysis of the effects of possible residential heat pump installation scenarios on the UK energy supply and carbon emissions. The monitoring study involved three ground source heat pump installations. The data collected consisted of heat output, electric power input, system temperatures and system status indicators. Analysis indicated that these systems showed reductions in carbon emissions from homes ranging from 18% to 37% compared with their counterfactual fuel-burning systems. The monitoring study provided empirical values to parameterise the heat pump model which was built around a linear regression relationship of heat pump COP to source / sink temperature differential based on heat pump performance data from standard laboratory test results. This model was added in a new module to enhance the BRE domestic energy model, BREDEM-8, which provides monthly estimates. Estimating rules were included for energy use from bivalent alternate, bivalent parallel operation and space cooling. The enhanced BREDEM-8 model was used to analyse the effects of possible residential heat pump installations within a housing stock energy model developed using the English Housing Survey datasets as a data source. Baseline estimates for the current stock were created using data reduction techniques to provide parameters (u-values, glazing details) for the enhanced BREDEM-8 model. Scenarios for heat pump deployments were created for the periods up to 2020 and 2050, selecting dwellings for heat pump application according to scenarios reflecting the perceived needs of the period, ie. the likely reduction in UK generating capacity up to 2020 and CO2 emissions reduction targets to 2050. Results showed that up to 2020, a policy of targeting dwellings with the highest overall emissions for replacement would reduce carbon emissions by 7.6%, at the expense of a 12% increase in electricity consumption. Targeting dwellings with the highest emitting existing systems caused a smaller increase in electricity consumption of about 6.5% with carbon emissions reduced by about 6.8%. The scenarios for the period to 2050, including 80% replacement of gas systems with heat pumps, gave an estimated 80% reduction in carbon emissions, when accompanied by an similar reduction in the carbon intensity of electricity generation and bringing about an increase in electricity consumption of somewhat over 40%. The effect of the more extreme scenario is to replace all but a small proportion of the energy used for heating and hot water with standard rate electricity, in 84.6% of the dwellings, and retaining gas in the remainder, 15.2%, bringing about a radical shift to electric heating throughout the housing stock