312 research outputs found

    Electron-Like Fermi Surface and Remnant (pi,0) Feature in Overdoped La1.78Sr0.22CuO4

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    We have performed an angle-resolved photoemission study of overdoped La1.78Sr0.22CuO4, and have observed sharp nodal quasiparticle peaks in the second Brillouin zone that are comparable to data from Bi2Sr2CaCu2O8+d. The data analysis using energy distribution curves, momentum distribution curves and intensity maps all show evidence of an electron-like Fermi surface, which is well explained by band structure calculations. Evidence for many-body effects are also found in the substantial spectral weight remaining below the Fermi level around (pi,0), where the band is predicted to lie above EF.Comment: 4 pages, 4 figure

    ARPES study of Pb doped Bi_2Sr_2CaCu_2O_8 - a new Fermi surface picture

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    High resolution angle resolved photoemission data from Pb doped Bi_2Sr_2CaCu_2O_8 (Bi2212) with suppressed superstructure is presented. Improved resolution and very high momentum space sampling at various photon energies reveal the presence of two Fermi surface pieces. One has the hole-like topology, while the other one has its van Hove singularity very close to (pi,0), its topology at some photon energies resembles the electron-like piece. This result provides a unifying picture of the Fermi surface in the Bi2212 compound and reconciles the conflicting reports.Comment: 4 pages, 4 figure

    Electron-Like Fermi Surface and Remnant (pi,0) Feature in Overdoped La1.78Sr0.22CuO4

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    We have performed an angle-resolved photoemission study of overdoped La1.78Sr0.22CuO4, and have observed sharp nodal quasiparticle peaks in the second Brillouin zone that are comparable to data from Bi2Sr2CaCu2O8+d. The data analysis using energy distribution curves, momentum distribution curves and intensity maps all show evidence of an electron-like Fermi surface, which is well explained by band structure calculations. Evidence for many-body effects are also found in the substantial spectral weight remaining below the Fermi level around (pi,0), where the band is predicted to lie above EF.Comment: 4 pages, 4 figure

    Evidence for an energy scale for quasiparticle dispersion in Bi_2Sr_2CaCu_2O_8

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    Quasiparticle dispersion in Bi2Sr2CaCu2O8Bi_{2}Sr_{2}CaCu_{2}O_{8} is investigated with improved angular resolution as a function of temperature and doping. Unlike the linear dispersion predicted by the band calculation, the data show a sharp break in dispersion at 50±1050\pm10 meVmeV binding energy where the velocity changes by a factor of two or more. This change provides an energy scale in the quasiparticle self-energy. This break in dispersion is evident at and away from the d-wave node line, but the magnitude of the dispersion change decreases with temperature and with increasing doping.Comment: 4 figure

    The symptom to assessment pathway for suspected chronic limb-threatening ischaemia (CLTI) affects quality of care: a process mapping exercise

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    Background: Delays in the pathway from first symptom to treatment of chronic limb-threatening ischaemia (CLTI) are associated with worse mortality and limb loss outcomes. This study examined the processes used by vascular services to provide urgent care to patients with suspected CLTI referred from the community. Methods: Vascular surgery units from various regions in England were invited to participate in a process mapping exercise. Clinical and non-clinical staff at participating units were interviewed, and process maps were created that captured key staff and structures used to create processes for referral receipt, triage and assessment at the units. Results: Twelve vascular units participated, and process maps were created after interviews with 45 participants. The units offered multiple points of access for urgent referrals from general practitioners and other community clinicians. Triage processes were varied, with units using different mixes of staff (including medical staff, podiatrists and s) and this led to processes of varying speed. The organisation of clinics to provide slots for ‘urgent’ patients was also varied, with some adopting hot clinics, while others used dedicated slots in routine clinics. Service organisation could be further complicated by separate processes for patients with and without diabetes, and because of the organisation of services regionally into vascular networks that had arterial and non-arterial centres. Conclusions: For referred patients with symptoms of CLTI, the points of access, triage and assessment processes used by vascular units are diverse. This reflects the local context and ingenuity of vascular units but can lead to complex processes. It is likely that benefits might be gained from simplification

    Dual Nature of the Electronic Structure of the Stripe Phase

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    High resolution angle-resolved photoemission measurements have been carried out on (La_1.4-xNd_0.6Sr_x)CuO_4, a model system with static stripes, and (La_1.85Sr_0.15)CuO_4, a high temperature superconductor (T_c=40K) with dynamic stripes. In addition to the straight segments near (pi, 0) and (0, pi) antinodal regions, we have identified the existence of nodal spectral weight and its associated Fermi surface in the electronic structure of both systems. The ARPES spectra in the nodal region show well-defined Fermi cut-off, indicating a metallic character of this charge-ordered state. This observation of nodal spectral weight, together with the straight segments near antinodal regions, reveals dual nature of the electronic structure of the stripes due to the competition of order and disorder

    A medical device-grade T1 and ECV phantom for global T1 mapping quality assurance - the T1_1 Mapping and ECV Standardization in cardiovascular magnetic resonance (T1MES) program

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    Background:\textbf{Background:} T1_1 mapping and extracellular volume (ECV) have the potential to guide patient care and serve as surrogate end-points in clinical trials, but measurements differ between cardiovascular magnetic resonance (CMR) scanners and pulse sequences. To help deliver T1_1 mapping to global clinical care, we developed a phantom-based quality assurance (QA) system for verification of measurement stability over time at individual sites, with further aims of generalization of results across sites, vendor systems, software versions and imaging sequences. We thus created T1MES: The T1 Mapping and ECV Standardization Program. Methods:\textbf{Methods:} A design collaboration consisting of a specialist MRI small-medium enterprise, clinicians, physicists and national metrology institutes was formed. A phantom was designed covering clinically relevant ranges of T1_1 and T2_2 in blood and myocardium, pre and post-contrast, for 1.5 T and 3 T. Reproducible mass manufacture was established. The device received regulatory clearance by the Food and Drug Administration (FDA) and Conformité Européene (CE) marking. Results:\textbf{Results:} The T1MES phantom is an agarose gel-based phantom using nickel chloride as the paramagnetic relaxation modifier. It was reproducibly specified and mass-produced with a rigorously repeatable process. Each phantom contains nine differently-doped agarose gel tubes embedded in a gel/beads matrix. Phantoms were free of air bubbles and susceptibility artifacts at both field strengths and T1_1 maps were free from off-resonance artifacts. The incorporation of high-density polyethylene beads in the main gel fill was effective at flattening the B1B_1 field. T1_1 and T2_2 values measured in T1MES showed coefficients of variation of 1 % or less between repeat scans indicating good short-term reproducibility. Temperature dependency experiments confirmed that over the range 15-30 °C the short-T1_1 tubes were more stable with temperature than the long-T1_1 tubes. A batch of 69 phantoms was mass-produced with random sampling of ten of these showing coefficients of variations for T1_1 of 0.64 ± 0.45 % and 0.49 ± 0.34 % at 1.5 T and 3 T respectively. Conclusion:\textbf{Conclusion:} The T1MES program has developed a T1_1 mapping phantom to CE/FDA manufacturing standards. An initial 69 phantoms with a multi-vendor user manual are now being scanned fortnightly in centers worldwide. Future results will explore T1_1 mapping sequences, platform performance, stability and the potential for standardization.This project has been funded by a European Association of Cardiovascular Imaging (EACVI part of the ESC) Imaging Research Grant, a UK National Institute of Health Research (NIHR) Biomedical Research Center (BRC) Cardiometabolic Research Grant at University College London (UCL, #BRC/ 199/JM/101320), and a Barts Charity Research Grant (#1107/2356/MRC0140). G.C. is supported by the National Institute for Health Research Rare Diseases Translational Research Collaboration (NIHR RD-TRC) and by the NIHR UCL Hospitals Biomedical Research Center. J.C.M. is directly and indirectly supported by the UCL Hospitals NIHR BRC and Biomedical Research Unit at Barts Hospital respectively. This work was in part supported by an NIHR BRC award to Cambridge University Hospitals NHS Foundation Trust and NIHR Cardiovascular Biomedical Research Unit support at Royal Brompton Hospital London UK

    Non-participation in population-based disease prevention programs in general practice

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    <p>Abstract</p> <p>Background</p> <p>The number of people with a chronic disease will strongly increase in the next decades. Therefore, prevention of disease becomes increasingly important. The aim of this systematic review was to identify factors that negatively influence participation in population-based disease prevention programs in General Practice and to establish whether the program type is related to non-participation levels.</p> <p>Methods</p> <p>We conducted a systematic review in Pubmed, EMBASE, CINAHL and PsycINFO, covering 2000 through July 6th 2012, to identify publications including information about characteristics of non-participants or reasons for non-participation in population-based disease prevention programs in General Practice.</p> <p>Results</p> <p>A total of 24 original studies met our criteria, seven of which focused on vaccination, eleven on screening aimed at early detection of disease, and six on screening aimed at identifying high risk of a disease, targeting a variety of diseases and conditions. Lack of personal relevance of the program, younger age, higher social deprivation and former non-participation were related to actual non-participation. No differences were found in non-participation levels or factors related to non-participation between the three program types. The large variation in non-participation levels within the program types may be partly due to differences in recruitment strategies, with more active, personalized strategies resulting in higher participation levels compared to an invitation letter.</p> <p>Conclusions</p> <p>There is still much to be gained by tailoring strategies to improve participation in those who are less likely to do so, namely younger individuals, those living in a deprived area and former non-participants. Participation may increase by applying more active recruitment strategies.</p
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