633 research outputs found

    Automated feedback control of body temperature for small animal studies with MR microscopy

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    Third-order relativistic many-body calculations of energies and lifetimes of levels along the silver isoelectronic sequence

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    Energies of 5l_j (l= s, p, d, f, g) and 4f_j states in neutral Ag and Ag-like ions with nuclear charges Z = 48 - 100 are calculated using relativistic many-body perturbation theory. Reduced matrix elements, oscillator strengths, transition rates and lifetimes are calculated for the 17 possible 5l_j-5l'_{j'} and 4f_j-5l_{j'} electric-dipole transitions. Third-order corrections to energies and dipole matrix elements are included for neutral Ag and for ions with Z60. Comparisons are made with available experimental data for transition energies and lifetimes. Correlation energies and transition rates are shown graphically as functions of nuclear charge Z for selected cases. These calculations provide a theoretical benchmark for comparison with experiment and theory.Comment: 8 page

    Mesh update techniques for free-surface flow solvers using spectral element method

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    This paper presents a novel mesh-update technique for unsteady free-surface Newtonian flows using spectral element method and relying on the arbitrary Lagrangian--Eulerian kinematic description for moving the grid. Selected results showing compatibility of this mesh-update technique with spectral element method are given

    BRAIN Α-TOCOPHEROL CONCENTRATION IS INVERSELY ASSOCIATED WITH NEUROFIBRILLARY TANGLE COUNTS IN BRAIN REGIONS AFFECTED IN EARLIER BRAAK STAGES: A CROSS-SECTIONAL FINDING IN THE OLDEST OLD

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    Objectives: Higher vitamin E status has been associated with lower risk of Alzheimer’s disease (AD). However, evidence of the association of vitamin E concentration in neural tissue with AD pathologies is limited. Design: The cross-sectional relationship between the human brain concentrations of α- and γ-tocopherol and the severity of AD pathologies – neurofibrillary tangle (NFT) and neuritic plaque (NP) – was investigated. Setting & Participants: Brains from 43 centenarians (≥ 98 years at death) enrolled in the Phase III of the Georgia Centenarian Study were collected at autopsy. Measurements: Brain α- and γ-tocopherol concentrations (previously reported) were averaged from frontal, temporal, and occipital cortices. NP and NFT counts (previously reported) were assessed in frontal, temporal, parietal, entorhinal cortices, amygdala, hippocampus, and subiculum. NFT topological progression was assessed using Braak staging. Multiple linear regression was performed to assess the relationship between tocopherol concentrations and NP or NFT counts, with and without adjustment for covariates. Results: Brain α-tocopherol concentrations were inversely associated with NFT but not NP counts in amygdala (β = -2.67, 95% CI [-4.57, -0.79]), entorhinal cortex (β = -2.01, 95% CI [-3.72, -0.30]), hippocampus (β = -2.23, 95% CI [-3.82, -0.64]), and subiculum (β = -2.52, 95% CI [-4.42, -0.62]) where NFT present earlier in its topological progression, but not in neocortices. Subjects with Braak III-IV had lower α-tocopherol (median = 69,622 pmol/g, IQR = 54,389-72,155 pmol/g) than those with Braak I-II (median = 72,108 pmol/g, IQR = 64,056-82,430 pmol/g), but the difference was of borderline significance (p = 0.063). γ-Tocopherol concentrations were not associated with either NFT or NP counts in any brain regions assessed. Conclusions: Higher brain α-tocopherol level is specifically associated with lower NFT counts in brain structures affected in earlier Braak stages. Our findings emphasize the possible importance of α-tocopherol intervention timing in tauopathy progression and warrant future clinical trials

    Transcatheter Closure of Paravalvular Defects Using a Purpose-Specific Occluder

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    ObjectivesThis study sought to describe a method of paravalvular leak closure using a purpose-specific occlusion device.BackgroundTranscatheter closure of paravalvular leaks has been hampered by technical challenges, the limitations of available imaging modalities, and the lack of closure devices specifically designed for this purpose.MethodsPatients with severe symptomatic paravalvular regurgitation at high risk for repeat surgery underwent transcatheter leak closure. Both left ventricular puncture and retrograde transfemoral approaches were used with fluoroscopic and 3-dimensional transesophageal guidance. A purpose-specific occluder (Vascular Plug III, AGA Medical Corp., Plymouth, Minnesota) was used.ResultsFive patients with severe prosthetic mitral and aortic paravalvular leaks underwent attempted closure. Implantation of the device was successfully accomplished in all. In 1 patient, the plug interfered with closure of a mechanical valve leaflet and was removed and replaced with an alternate device. Complications included pericardial bleeding in 2 patients with a transapical approach. There was no procedural mortality. At a median follow-up of 191 days (interquartile range [IQR] 169 to 203 days) all patients were alive. New York Heart Association functional class fell from 4 (IQR 3 to 4) to 2 (IQR 2 to 3), hemoglobin rose from 89 g/l (IQR 87 to 108 g/l) to 115 g/l (IQR 104 to 118 g/l), creatinine fell from 109 ÎĽmol/l (IQR 106 to 132 ÎĽmol/l) to 89 ÎĽmol/l (IQR 89 to 126 ÎĽmol/l). Median echocardiographic follow-up at 58 days (IQR 56 to 70 days) reported residual regurgitation to be reduced from grade 4 to grade 2 (IQR 1.5 to 2.25).ConclusionsClosure of mitral and aortic prosthetic paravalvular leaks with the Vascular Plug III using either a transapical (mitral) or a retrograde (aortic) approach appears promising

    Quantized Thermal Transport in the Fractional Quantum Hall Effect

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    We analyze thermal transport in the fractional quantum Hall effect (FQHE), employing a Luttinger liquid model of edge states. Impurity mediated inter-channel scattering events are incorporated in a hydrodynamic description of heat and charge transport. The thermal Hall conductance, KHK_H, is shown to provide a new and universal characterization of the FQHE state, and reveals non-trivial information about the edge structure. The Lorenz ratio between thermal and electrical Hall conductances {\it violates} the free-electron Wiedemann-Franz law, and for some fractional states is predicted to be {\it negative}. We argue that thermal transport may provide a unique way to detect the presence of the elusive upstream propagating modes, predicted for fractions such as ν=2/3\nu=2/3 and ν=3/5\nu=3/5.Comment: 6 pages REVTeX, 2 postscript figures (uuencoded and compressed

    Vacuum polarization calculations for hydrogenlike and alkalilike ions

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    Complete vacuum polarization calculations incorporating finite nuclear size are presented for hydrogenic ions with principal quantum numbers n=1-5. Lithiumlike, sodiumlike, and copperlike ions are also treated starting with Kohn-Sham potentials, and including first-order screening corrections. In both cases dominant Uehling terms are calculated with high accuracy, and smaller Wichmann- Kroll terms are obtained using numerical electron Green's functions.Comment: 23 pages, 1 figur

    Mechanistic insights into the C<sub>55</sub>-P targeting lipopeptide antibiotics revealed by structure-activity studies and high-resolution crystal structures

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    AbstractThe continued rise of antibiotic resistance is a global concern that threatens to undermine many aspects of modern medical practice. Key to addressing this threat is the discovery and development of new antibiotics that operate by unexploited modes of action. The so-called calcium-dependent lipopeptide antibiotics (CDAs) are an important emerging class of natural products that provides a source of new antibiotic agents rich in structural and mechanistic diversity. Notable in this regard is the subset of CDAs comprising the laspartomycins and amphomycins/friulimicins that specifically target the bacterial cell wall precursor undecaprenyl phosphate (C55-P). In this study we describe the design and synthesis of new C55-P-targeting CDAs with structural features drawn from both the laspartomycin and amphomycin/friulimicin classes. Assessment of these lipopeptides revealed previously unknown and surprisingly subtle structural features that are required for antibacterial activity. High-resolution crystal structures further indicate that the amphomycin/friulimicin-like lipopeptides adopt a unique crystal packing that governs their interaction with C55-P and provides an explanation for their antibacterial effect. In addition, live-cell microscopy studies provide further insights into the biological activity of the C55-P targeting CDAs highlighting their unique mechanism of action relative to the clinically used CDA daptomycin.Microbial Biotechnolog
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