Structural and electronic properties of fulleride superconductors

In the present thesis, I discuss some of the current advances in research in the field of the solid state science of fullerenes. The reaction of C60 with alkali metals using both conventional solid state and low temperature solution-based synthesis techniques has led to the production of fulleride salts with interesting structural and superconducting properties. In superconducting A3C60 systems, it has been widely reported that Tc increases monotonically with interfulleride separation. Of particular interest is the family Na2Rb1-xCsxC60 (0 ≤ x ≤ 1) as they display a much steeper rate of change of Tc with interfulleride spacing. Here we discuss the related family of quaternary fullerides, Na2-xKxCsC60 in an attempt to explore the consequences of this trend and produce fulleride salts with elevated Tc's In addition, the monotonic increase in Tc with increasing interfulleride separation has driven attempts towards the synthesis of new superconducting fullerides with very large lattice parameters. A key material among the A3C60 systems is the end member, Cs3C60, which has remained elusive in attempts to synthesise it by traditional solid state techniques due to the thermodynamic instability of this phase caused by the accommodation of the large Cs+ ion (r = 1.67 Å) in the small tetrahedral holes (r = 1.12 Å). Here we report the synthesis of “FCC rich” and "A15 rich" samples of the series, RbxCs3-xC60 (0.0 ≤ x ≤ 0.5) via low temperature synthetic techniques utilising the solvents ammonia and methylamine, respectively. This allowed us to study the effects of both chemical (by partial substitution of Cs+ by the smaller Rb+ cation) and physical pressure upon the electronic and superconducting properties of these materials. For all samples, detailed structural studies have been performed using synchrotron X-ray powder diffraction and magnetic behaviour using SQUID magnetometry techniques

Projections of the current and future disease burden of hepatitis C virus infection in Malaysia

The prevalence of hepatitis C virus (HCV) infection in Malaysia has been estimated at 2.5% of the adult population. Our objective, satisfying one of the directives of the WHO Framework for Global Action on Viral Hepatitis, was to forecast the HCV disease burden in Malaysia using modelling methods.An age-structured multi-state Markov model was developed to simulate the natural history of HCV infection. We tested three historical incidence scenarios that would give rise to the estimated prevalence in 2009, and calculated the incidence of cirrhosis, end-stage liver disease, and death, and disability-adjusted life-years (DALYs) under each scenario, to the year 2039. In the baseline scenario, current antiviral treatment levels were extended from 2014 to the end of the simulation period. To estimate the disease burden averted under current sustained virological response rates and treatment levels, the baseline scenario was compared to a counterfactual scenario in which no past or future treatment is assumed.In the baseline scenario, the projected disease burden for the year 2039 is 94,900 DALYs/year (95% credible interval (CrI): 77,100 to 124,500), with 2,002 (95% CrI: 1340 to 3040) and 540 (95% CrI: 251 to 1,030) individuals predicted to develop decompensated cirrhosis and hepatocellular carcinoma, respectively, in that year. Although current treatment practice is estimated to avert a cumulative total of 2,200 deaths from DC or HCC, a cumulative total of 63,900 HCV-related deaths is projected by 2039.The HCV-related disease burden is already high and is forecast to rise steeply over the coming decades under current levels of antiviral treatment. Increased governmental resources to improve HCV screening and treatment rates and to reduce transmission are essential to address the high projected HCV disease burden in Malaysia

Boolean Delay Equations: A simple way of looking at complex systems

Boolean Delay Equations (BDEs) are semi-discrete dynamical models with Boolean-valued variables that evolve in continuous time. Systems of BDEs can be classified into conservative or dissipative, in a manner that parallels the classification of ordinary or partial differential equations. Solutions to certain conservative BDEs exhibit growth of complexity in time. They represent therewith metaphors for biological evolution or human history. Dissipative BDEs are structurally stable and exhibit multiple equilibria and limit cycles, as well as more complex, fractal solution sets, such as Devil's staircases and ``fractal sunbursts``. All known solutions of dissipative BDEs have stationary variance. BDE systems of this type, both free and forced, have been used as highly idealized models of climate change on interannual, interdecadal and paleoclimatic time scales. BDEs are also being used as flexible, highly efficient models of colliding cascades in earthquake modeling and prediction, as well as in genetics. In this paper we review the theory of systems of BDEs and illustrate their applications to climatic and solid earth problems. The former have used small systems of BDEs, while the latter have used large networks of BDEs. We moreover introduce BDEs with an infinite number of variables distributed in space (``partial BDEs``) and discuss connections with other types of dynamical systems, including cellular automata and Boolean networks. This research-and-review paper concludes with a set of open questions.Comment: Latex, 67 pages with 15 eps figures. Revised version, in particular the discussion on partial BDEs is updated and enlarge

Children's travel to school—the interaction of individual, neighbourhood and school factors

The increase in average distance from home to secondary school over recent decades has been accompanied by a significant growth in the proportion of pupils travelling to school by motorized means as opposed to walking or cycling. More recently this switch in travel mode has received considerable attention as declining levels of physical activity, growing car dependence and the childhood obesity “crisis” have pushed concerns about the health of future generations up the public health agenda, particularly in the U.S., but also in the UK and Europe. This has led to a proliferation of international studies researching a variety of individual, school and spatial characteristics associated with children's active travel to school which has been targeted by some governments as a potential silver bullet to reverse the trend. However, to date national pupil census data, which comprises annual data on all English pupils, including a mode of travel to school variable, has been under-utilised in the analysis of how pupils commute to school. Furthermore, methodologically, the grouped nature of the data with pupils clustered within both schools and residential neighbourhoods has often been ignored - an omission which can have considerable consequences for the statistical estimation of the model. The research presented here seeks to address both of these points by analysing pupil census data on all 26,709 secondary pupils (aged 11-16) who attended schools in Sheffield, UK during the 2009-10. Individual pupil data is grouped within school, and neighbourhood, within a cross-classified multilevel model of active versus motorised modes of commuting to school. The results support the findings of other research that distance to school is key, but find that sociospatial clustering within neighbourhoods and schools are also critical. A further finding is that distance to school varies significantly by ethnicity, with white British pupils travelling the shortest distance of all ethnic groups. The implications of these findings for education and transport policy are discussed

Facilitating knowledge exchange between health-care sectors, organisations and professions: A longitudinal mixed-methods study of boundary-spanning processes and their impact on health-care quality

Background: Relatively little is known about how people and groups who function in boundary-spanning positions between different sectors, organisations and professions contribute to improved quality of health care and clinical outcomes. Objectives: To explore whether or not boundary-spanning processes stimulate the creation and exchange of knowledge between sectors, organisations and professions and whether or not this leads, through better integration of services, to improvements in the quality of care. Design: A 2-year longitudinal nested case study design using mixed methods. Setting: An inner-city area in England (‘Coxford’) comprising 26 general practices in ‘Westpark’ and a comparative sample of 57 practices. Participants: Health-care and non-health-care practitioners representing the range of staff participating in the Westpark Initiative (WI) and patients. Interventions: The WI sought to improve services through facilitating knowledge exchange and collaboration between general practitioners, community services, voluntary groups and acute specialists during the period late 2009 to early 2012. We investigated the impact of the four WI boundary-spanning teams on services and the processes through which they produced their effects. Main outcome measures: (1) Quality-of-care indicators during the period 2008–11; (2) diabetes admissions data from April 2006 to December 2011, adjusted for deprivation scores; and (3) referrals to psychological therapies from January 2010 to March 2012. Data sources: Data sources included 42 semistructured staff interviews, 361 hours of non-participant observation, 36 online diaries, 103 respondents to a staff survey, two patient focus groups and a secondary analyses of local and national data sets. Results: The four teams varied in their ability to, first, exchange knowledge across boundaries and, second, implement changes to improve the integration of services. The study setting experienced conditions of flux and uncertainty in which known horizontal and vertical structures underwent considerable change and the WI did not run its course as originally planned. Although knowledge exchanges did occur across sectoral, organisational and professional boundaries, in the case of child and family health services, early efforts to improve the integration of services were not sustained. In the case of dementia, team leadership and membership were undermined by external reorganisations. The anxiety and depression in black and minority ethnic populations team succeeded in reaching its self-defined goal of increasing referrals from Westpark practices to the local well-being service. From October to December 2010 onwards, referrals have been generally higher in the six practices with a link worker than in those without, but the performance of Westpark and Coxford practices did not differ significantly on three national quality indicators. General practices in a WI diabetes ‘cluster’ performed better on three of 17 Quality and Outcomes Framework (QOF) indicators than practices in the remainder of Westpark and in the wider Coxford primary care trust. Surprisingly, practices in Westpark, but not in the diabetes cluster, performed better on one indicator. No statistically significant differences were found on the remaining 13 QOF indicators. The time profiles differed significantly between the three groups for elective and emergency admissions and bed-days. Conclusions: Boundary spanning is a potential solution to the challenge of integrating health-care services and we explored how such processes perform in an ‘extreme case’ context of uncertainty. Although the WI may have been a necessary intervention to enable knowledge exchange across a range of boundaries, it was not alone sufficient. Even in the face of substantial challenges, one of the four teams was able to adapt and build resilience. Implications for future boundary-spanning interventions are identified. Future research should evaluate the direct, measurable and sustained impact of boundary-spanning processes on patient care outcomes (and experiences), as well as further empirically based critiques and reconceptualisations of the socialisation→externalisation→combination→internalisation (SECI) model, so that the implications can be translated into practical ideas developed in partnership with NHS managers. Funding: The National Institute for Health Research Health Services and Delivery Research programme

The contrasting role of male relatedness in different mechanisms of sexual selection in red junglefowl

In structured populations, competition for reproductive opportunities should be relaxed among related males. The few tests of this prediction often neglect the fact that sexual selection acts through multiple mechanisms, both before and after mating. We performed experiments to study the role of within-group male relatedness across pre- and postcopulatory mechanisms of sexual selection in social groups of red junglefowl, Gallus gallus, in which two related males and one unrelated male competed over females unrelated to all the males. We confirm theoretical expectations that, after controlling for male social status, competition over mating was reduced among related males. However, this effect was contrasted by other sexual selection mechanisms. First, females biased male mating in favor of the unrelated male, and might also favor his inseminations after mating. Second, males invested more—rather than fewer—sperm in postcopulatory competition with relatives. A number of factors may contribute to explain this counterintuitive pattern of sperm allocation, including trade-offs between male investment in pre- versus postcopulatory competition, differences in the relative relatedness of pre- versus postcopulatory competitors, and female bias in sperm utilization in response to male relatedness. Collectively, these results reveal that within-group male relatedness may have contrasting effects in different mechanisms of sexual selection

High-spectral-resolution Observations of the Optical Filamentary Nebula Surrounding NGC 1275

We present new high-spectral-resolution observations (R = λ/Δλ = 7000) of the filamentary nebula surrounding NGC 1275, the central galaxy of the Perseus cluster. These observations have been obtained with SITELLE, an imaging Fourier transform spectrometer installed on the Canada–France–Hawai Telescope with a field of view of 11′×11′ , encapsulating the entire filamentary structure of ionized gas despite its large size of 80 kpc × 50 kpc. Here, we present renewed fluxes, velocities, and velocity dispersion maps that show in great detail the kinematics of the optical nebula at [S ii] λ6716, [S ii] λ6731, [N ii] λ6584, Hα (6563 Å), and [N ii] λ6548. These maps reveal the existence of a bright flattened disk-shaped structure in the core extending to r ∼10 kpc and dominated by a chaotic velocity field. This structure is located in the wake of X-ray cavities and characterized by a high mean velocity dispersion of 134 km s−1. The disk-shaped structure is surrounded by an extended array of filaments spread out to r ∼ 50 kpc that are 10 times fainter in flux, remarkably quiescent, and have a uniform mean velocity dispersion of 44 km s−1. This stability is puzzling given that the cluster core exhibits several energetic phenomena. Based on these results, we argue that there are two mechanisms that form multiphase gas in clusters of galaxies: a first triggered in the wake of X-ray cavities leading to more turbulent multiphase gas and a second, distinct mechanism, that is gentle and leads to large-scale multiphase gas spreading throughout the core