High-temperature superconductivity in a family of iron pnictide materials

The work in this thesis falls roughly into three parts, which I characterise loosely as a developmental stage, an exploratory stage, and an attempt to contribute to understanding of the field. In the developmental stage, I have worked to design a variety of methods to create high-quality samples of various Iron Pnictide superconductors, to dope them with various chemicals and to characterise the resulting crystalline samples. I discuss in depth the signature of good quality crystals and the various experiments that they have been used in by myself and my collaborators. These processes are ongoing and will hopefully continue to contribute to my research group’s capabilities. My exploratory work involves a detailed survey of one particular family, Sr(Fe1−xCox)2As2, as the level of Cobalt is varied, and the mapping of the phase diagram for the system. I have also made a comparison to the better-measured Barium analogue, and discuss the reasons for the differences in character between the two, most notably the lack of a splitting of the structural and magnetic transitions in the first species. I also discuss the effect of pressure, which can lead to superconductivity in lightly doped samples for very modest pressures; and annealing, which increases transition temperatures within samples, on a limited quantity of crystals. Finally, I attempt to contribute to the understanding of the field via a series of Resonant Ultrasound Spectroscopic experiments conducted by a collaborator on my crystals and analysed by me. I see distinct first-order transitions in the parent compounds, characterisable above the high-T structural transition within a Ginzburg-Landau pseudoproper ferroelastic scheme for a transition coupling weakly to strain but driven by another order parameter. My observations allow several statements about the symmetry of the order parameter and are suggestive of a non-magnetically driven structural transition. In the case of doped samples a much richer behavior is seen, with a broad transition and simultaneous relaxation of all elastic peaks and a broad temperature range of significant dispersion. The effect of the softening is seen far above TN and lends strong support to the familiy of models predicting such high-T fluctuations.PhD Studentship funded by EPSRC; Jack Gillett also thanks Trinity College for support and accommodation during studentship

Superconductivity up to 29 K in SrFe2As2 and BaFe2As2 at high pressures

We report the discovery of superconductivity at high pressure in SrFe2As2 and BaFe2As2. The superconducting transition temperatures are up to 27 K in SrFe2As2 and 29 K in BaFe2As2, making these the highest pressure-induced superconducting materials discovered thus far.Comment: Accepted in Journal of Physics: Condensed Matte

Reproductive fitness and genetic risk of psychiatric disorders in the general population.

To access publisher's full text version of this article, please click on the hyperlink in Additional Links field or click on the hyperlink at the top of the page marked FilesThe persistence of common, heritable psychiatric disorders that reduce reproductive fitness is an evolutionary paradox. Here, we investigate the selection pressures on sequence variants that predispose to schizophrenia, autism, bipolar disorder, major depression and attention deficit hyperactivity disorder (ADHD) using genomic data from 150,656 Icelanders, excluding those diagnosed with these psychiatric diseases. Polygenic risk of autism and ADHD is associated with number of children. Higher polygenic risk of autism is associated with fewer children and older age at first child whereas higher polygenic risk of ADHD is associated with having more children. We find no evidence for a selective advantage of a high polygenic risk of schizophrenia or bipolar disorder. Rare copy-number variants conferring moderate to high risk of psychiatric illness are associated with having fewer children and are under stronger negative selection pressure than common sequence variants.European Community's Seventh Framework Programme under the Marie Curie Industry-Academia Partnership and Pathways (PsychDPC) Innovative Medicines Initiative Joint Undertaking National Institute for Health Research (NIHR) Biomedical Research Centre for Mental Health at South London Maudsley NHS Foundation Trust King's College Londo

Osteoprotegerin antibodies in the pathogenesis of osteoporosis

Osteoporosis is a common complication of many autoimmune diseases that is typically attributed to disease specific factors rather than a direct autoimmune process. This thesis arises from the investigation of a patient with severe high bone turnover osteoporosis who was identified as having autoimmune disease but whose osteoporosis deteriorated despite appropriate treatment. This presentation led to the hypothesis that neutralising autoantibodies to the bone protective cytokine osteoprotegerin (OPG) may have developed. Serum from the index patient, but not healthy controls, was able to immunoprecipitate recombinant OPG protein, demonstrating that OPG had become the target of an autoimmune response. Purified immunoglobulins from the index case were able to inhibit the function of OPG in vitro, by suppressing OPG-mediated inhibition of a luciferase reporter cell line. This represents the first description of disease associated with neutralising antibodies to OPG. Whilst the immunoprecipitation assay did identify OPG antibodies in further patients these results were difficult to quantify. A more robust enzyme linked immunosorbent assay for OPG antibodies was developed using OPG as a capture antigen, which allowed the screening of patient cohorts. Presence of OPG antibodies was defined as a titre greater than the mean plus three standard deviations of 101 healthy volunteers. A low prevalence of 14/864 (1.6%) was seen in a general population cohort and no association with bone density or turnover was seen. An association with higher vascular calcification score in this cohort requires replication. A prevalence of 37/315 (11.7%) was seen in an osteoporosis cohort though no association was seen with bone density or response to treatment. In a coeliac cohort OPG antibodies were identified in 14/282 (5.0%) patients and presence of antibody was independently associated with reduced spine bone density. Functional inhibition of OPG was shown in vitro in 3/14 (21.4%) of the positive cases. Case finding of osteoporosis in the coeliac cohort was not improved by identification of OPG antibodies. These results are consistent with OPG antibodies being pathological in a small number of patients with osteoporosis but a clinical utility of measuring OPG antibodies has not been established

Diabetes self-management arrangements in Europe: a realist review to facilitate a project implemented in six countries

Background: Self-management of long term conditions can promote quality of life whilst delivering benefits to the financing of health care systems. However, rarely are the meso-level influences, likely to be of direct relevance to these desired outcomes, systematically explored. No specific international guidelines exist suggesting the features of the most appropriate structure and organisation of health care systems within which to situate self-management approaches and practices. This review aimed to identify the quantitative literature with regard to diabetes self-management arrangements currently in place within the health care systems of six countries (The United Kingdom, The Netherlands, Norway, Spain, Bulgaria, and Greece) and explore how these are integrated into the broader health care and welfare systems in each country. Methods: The methodology for a realist review was followed. Publications of interest dating from 2000 to 2013 were identified through appropriate MeSH terms by a systematic search in six bibliographic databases. A search diary was maintained and the studies were assessed for their quality and risk of bias. Results: Following the multi-step search strategy, 56 studies were included in the final review (the majority from the UK) reporting design methods and findings on 21 interventions and programmes for diabetes and chronic disease self-management. Most (11/21, 52%) of the interventions were designed to fit within the context of primary care. The majority (11/21, 52%) highlighted behavioural change as an important goal. Finally, some (5/21, 24%) referred explicitly to Internet-based tools. Conclusions: This review is based on results which are derived from a total of at least 5,500 individuals residing in the six participating countries. It indicates a policy shift towards patient-centred self-management of diabetes in a primary care context. The professional role of diabetes specialist nurses, the need for multidisciplinary approaches and a focus on patient education emerge as fundamental principles in the design of relevant programmes. Socio-economic circumstances are relevant to the capacity to self-manage and suggest that any gains and progress will be hard to maintain during economic austerity. This realist review should be interpreted within the wider context of a whole systems approach regarding self-care support and chronic illness management

Geography revision

Utiliza imaginativas situaciones de la vida real para ayudar a los estudiantes de doce y trece años a comprender y recordar lo esencial de la etapa clave 3 (Key Stage 3) de Geografía. Este planteamiento refleja el actual cambio en el método de enseñanza que hace énfasis en un aprendizaje contextualizado, es decir, el aprendizaje acerca de las cosas dentro de una situación relevante. Entreteje personajes humorísticos, escenarios de la vida real, rompecabezas y actividades con ejercicios de aprendizaje más formal. Cada tres actividades hay un test de conocimientos. Tiene glosario, respuestas a los pasatiempos y a los tests de conocimientos.SCBiblioteca de Educación del Ministerio de Educación, Cultura y Deporte; Calle San Agustín, 5 - 3 planta; 28014 Madrid; Tel. +34917748000; [email protected]

An exploration into the relationships between paranormal belief and belief in precognitive dreams with propensity to relate unrelated events and creativity

The present study aimed to study the relationships between paranormal belief and belief in precognitive dreams with propensity to connect unrelated events and creativity. There were 50 participants who took part in the study and their paranormal belief score was measured using the revised paranormal belief scale (RPBS) (Tobacyk, 2004) in accordance with the two factor model proposed by Lange, Irwin & Houran (2000). Their belief in precognitive dreams score was measured using a questionnaire with items from Schredl (2004) and Watt & Valášek (2011). Both paranormal belief and belief in precognitive dreams scores were correlated, using Pearson’s product moment correlations, with propensity to connect unrelated events, as measured by a novel connections task inspired by Madey (1993), and creativity, as measured by the bridge-the-associative-gap (BAG) task (Gianotti, Mohr, Pizzagalli, Lehmann & Brugger, 2001). There was a significant positive relationship between paranormal belief score and belief in precognitive dream score with connection task score leading to the conclusion that paranormal belief and belief in precognitive dreams are positively and significantly related to propensity to connect unrelated events. There were no significant positive relationships between paranormal belief score and belief in precognitive dreams score with creativity but due to the wealth of research that suggests a link between paranormal belief and creativity, it was concluded that the lack of a significant relationship was likely due to problems with the BAG task

Algorithms and Probabilistic Bounds for the Chromatic Number of Random Composite Graphs

The composite graph coloring problem (CGCP) is a generalization of the standard graph coloring problem (SGCP). Associated with each vertex is a positive integer called its chromaticity. The chromaticity of a vertex specifies the number of consecutive colors which must be assigned to it. An exact algorithm for solving the CGCP is presented. The algorithm is a generalization of the vertex-sequential with dynamic reordering approach for the SGCP. It is shown that the method is as effective on composite graphs as its counterpart is on standard graphs. Let X̅(CGnp) and X̅(SGnp) denote, respectively, the mean chromatic number of a sample of random composite and standard graphs of order n and edge density p. It is demonstrated that the ratio X̅(CGnp) √X(SGnp), depends on p, but, for fixed p, is essentially constant, over the range of values of n for which the algorithms were applied. Several new heuristic methods for efficiently approximating X(CGnp) for large values of n are presented. Of these, the CDsatur and CDsaturl1 algorithms, which are generalizations of the well known Dsatur algorithm, are shown to be very competitive with previously tested procedures. A known method for calculating probabilistic lower bounds for X̅(SGnp) is generalized to produce such bounds for X̅(CGnp). Also, a method for estimating the value of X(SGnp), is shown to produce probabilistic upper bounds for X̅(SGnp). This procedure is then generalized to a method for calculating probabilistic upper bounds for X̅(CGnp). The resulting bounds are used to evaluate the actual effectiveness of several heuristic algorithms. It is shown that, for fixed p, although the mean absolute error of the heuristic procedures appears to increase as n is varied from 100 to 1000, the mean relative error remains reasonably constant