1,118 research outputs found

    Localized electronic states and photoemission superconducting condensate in Bi2_{2}Sr2_{2}Ca1_{1}Cu2_{2}O8+x_{8+x}

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    We present the first detailed angle-resolved photoemission evidence that there are two types of carriers that contribute to the photoemission superconducting condensate in Bi2Sr2Ca1Cu2O8+xBi_{2}Sr_{2}Ca_{1}Cu_{2}O_{8+x}. Our data indicate that both itinerant and somewhat localized normal state carriers can contribute to the formation of Cooper pairs.Comment: APS_Revtex, 11 pages, including 3 figures, available upon request. UW-Madison preprint#

    Experimental characterisation of a novel phase change material heat storage unit for state-of-charge estimation

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    Energy storage methods will be a critical part of the future energy supply system, as demand is increased by electrification of domestic heat and take-up of renewable generation increases the variability of supply. Domestic storage units are likely to be key to this transition, and this paper will present investigations into a unit for storage of domestic heat. A phase change material (PCM) heat storage unit has been developed that has the potential to provide effective heat storage facility in a domestic capacity. Effective control and use of the storage units is dependent on accurate state-of-charge (SoC) estimation, tools for which are being developed and supported by data presented in this paper. A novel test bed has been developed in order to acquire data for this purpose. The rig is situated in a temperature-controlled chamber which enables charge and discharge tests at a range of ambient temperatures. Automated control of the rig is also available, which allows for repeatable tests to be carried out to gather data for model development

    Defining biodiverse reforestation: Why it matters for climate change mitigation and biodiversity

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    Reforestation to capture and store atmospheric carbon is increasingly championed as a climate change mitigation policy response. Reforestation plantings have the potential to provide conservation co-benefits when diverse mixtures of native species are planted, and there are growing attempts to monetise biodiversity benefits from carbon reforestation projects, particularly within emerging carbon markets. But what is meant by ‘biodiverse’ across different stakeholders and groups implementing and overseeing these projects and how do these perceptions compare with long-standing scientific definitions? Here, we discuss approaches to, and definitions of, biodiversity in the context of reforestation for carbon sequestration. Our aim is to review how the concept of biodiversity is defined and applied among stakeholders (e.g., governments, carbon certifiers and farmers) and rights holders (i.e., First Nations people) engaging in reforestation, and to identify best-practice methods for restoring biodiversity in these projects. We find that some stakeholders have a vague understanding of diversity across varying levels of biological organisation (genes to ecosystems). While most understand that biodiversity underpins ecosystem functions and services, many stakeholders may not appreciate the difficulties of restoring biodiversity akin to reference ecosystems. Consequently, biodiversity goals are rarely explicit, and project goals may never be achieved because the levels of restored biodiversity are inadequate to support functional ecosystems and desired ecosystem services. We suggest there is significant value in integrating biodiversity objectives into reforestation projects and setting specific restoration goals with transparent reporting outcomes will pave the way for ensuring reforestation projects have meaningful outcomes for biodiversity, and legitimate incentive payments for biodiversity and natural capital accounting

    Schur Polynomials and the Yang-Baxter equation

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    We show that within the six-vertex model there is a parametrized Yang-Baxter equation with nonabelian parameter group GL(2)xGL(1) at the center of the disordered regime. As an application we rederive deformations of the Weyl character formule of Tokuyama and of Hamel and King.Comment: Revised introduction; slightly changed reference

    Ab initio study of the beta$-tin->Imma->sh phase transitions in silicon and germanium

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    We have investigated the structural sequence of the high-pressure phases of silicon and germanium. We have focussed on the cd->beta-tin->Imma->sh phase transitions. We have used the plane-wave pseudopotential approach to the density-functional theory implemented within the Vienna ab-initio simulation package (VASP). We have determined the equilibrium properties of each structure and the values of the critical parameters including a hysteresis effect at the phase transitions. The order of the phase transitions has been obtained alternatively from the pressure dependence of the enthalpy and of the internal structure parameters. The commonly used tangent construction is shown to be very unreliable. Our calculations identify a first-order phase transition from the cd to the beta-tin and from the Imma to the sh phase, and they indicate the possibility of a second-order phase-transition from the beta-tin to the Imma phase. Finally, we have derived the enthalpy barriers between the phases.Comment: 12 pages, 16 figure

    Two-loop corrections to the decay rate of parapositronium

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    Order α2\alpha^2 corrections to the decay rate of parapositronium are calculated. A QED scattering calculation of the amplitude for electron-positron annihilation into two photons at threshold is combined with the technique of effective field theory to determine an NRQED Hamiltonian, which is then used in a bound state calculation to determine the decay rate. Our result for the two-loop correction is 5.1243(33)5.1243(33) in units of (α/π)2(\alpha/\pi)^2 times the lowest order rate. This is consistent with but more precise than the result 5.1(3)5.1(3) of a previous calculation.Comment: 26 pages, 7 figure

    Consistent Anisotropic Repulsions for Simple Molecules

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    We extract atom-atom potentials from the effective spherical potentials that suc cessfully model Hugoniot experiments on molecular fluids, e.g., O2O_2 and N2N_2. In the case of O2O_2 the resulting potentials compare very well with the atom-atom potentials used in studies of solid-state propertie s, while for N2N_2 they are considerably softer at short distances. Ground state (T=0K) and room temperatu re calculations performed with the new NNN-N potential resolve the previous discrepancy between experimental and theoretical results.Comment: RevTeX, 5 figure

    Rare variants in optic disc area gene CARD10 enriched in primary open-angle glaucoma

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    Background: Genome-wide association studies (GWAS) have identified association of common alleles with primary open-angle glaucoma (POAG) and its quantitative endophenotypes near numerous genes. This study aims to determine whether rare pathogenic variants in these disease-associated genes contribute to POAG. Methods: Participants fulfilled strict inclusion criteria of advanced POAG at a young age of diagnosis. Myocilin mutation carriers were excluded using direct sequencing. Whole exome sequencing was performed on 187 glaucoma cases and 103 local screened nonglaucoma controls then joint-called with exomes of 993 previously sequenced Australian controls. GWAS-associated genes were assessed for enrichment of rare predicted pathogenic variants in POAG. Significantly enriched genes were compared against Exome Aggregation Consortium (ExAC) public control. Results: Eighty-six GWAS disease or trait-associated glaucoma genes were captured and sequenced. CARD10 showed enrichment after Bonferroni correction for rare variants in glaucoma cases (OR = 13.2, P = 6.94 × 10−5) with mutations identified in 4.28% of our POAG cohort compared to 0.27% in controls. CARD10 was significantly associated with optic disc parameters in previous GWAS. The whole GWAS gene set showed no enrichment in POAG overall (OR = 1.12, P = 0.51). Conclusion: We report here an enrichment of rare predicted pathogenic coding variants within a GWAS-associated locus in POAG (CARD10). These findings indicate that both common and rare pathogenic coding variants in CARD10 may contribute to POAG pathogenesis.Tiger Zhou, Emmanuelle Souzeau, Shiwani Sharma, Owen M. Siggs, Ivan Goldberg, Paul R. Healey, Stuart Graham, Alex W. Hewitt, David A. Mackey, Robert J. Casson, John Landers, Richard Mills, Jonathan Ellis, Paul Leo, Matthew A. Brown, Stuart MacGregor, Kathryn P. Burdon and Jamie E. Crai

    Development of a patient reported outcome measure for fatigue in motor neurone disease: the Neurological Fatigue Index (NFI-MND).

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    BACKGROUND: The objective of this research was to develop a disease-specific measure for fatigue in patients with motor neurone disease (MND) by generating data that would fit the Rasch measurement model. Fatigue was defined as reversible motor weakness and whole-body tiredness that was predominantly brought on by muscular exertion and was partially relieved by rest. METHODS: Qualitative interviews were undertaken to confirm the suitability of a previously identified set of 52 neurological fatigue items as relevant to patients with MND. Patients were recruited from five U.K. MND clinics. Questionnaires were administered during clinic or by post. A sub-sample of patients completed the questionnaire again after 2-4 weeks to assess test-retest validity. Exploratory factor analyses and Rasch analysis were conducted on the item set. RESULTS: Qualitative interviews with ten MND patients confirmed the suitability of 52 previously identified neurological fatigue items as relevant to patients with MND. 298 patients consented to completing the initial questionnaire including this item set, with an additional 78 patients completing the questionnaire a second time after 4-6 weeks. Exploratory Factor Analysis identified five potential subscales that could be conceptualised as representing: 'Energy', 'Reversible muscular weakness' (shortened to 'Weakness'), 'Concentration', 'Effects of heat' and 'Rest'. Of the original five factors, two factors 'Energy' and 'Weakness' met the expectations of the Rasch model. A higher order fatigue summary scale, consisting of items from the 'Energy' and 'Weakness' subscales, was found to fit the Rasch model and have acceptable unidimensionality. The two scales and the higher order summary scale were shown to fulfil model expectations, including assumptions of unidimensionality, local independency and an absence of differential item functioning. CONCLUSIONS: The Neurological Fatigue Index for MND (NFI-MND) is a simple, easy-to-administer fatigue scale. It consists of an 8-item fatigue summary scale in addition to separate scales for measuring fatigue experienced as reversible muscular weakness and fatigue expressed as feelings of low energy and whole body tiredness. The underlying two factor structure supports the patient concept of fatigue derived from qualitative interviews in this population. All three scales were shown to be reliable and capable of interval level measurement
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