597 research outputs found
Vortex shear effects in layered superconductors
Motivated by recent transport and magnetization measurements in BSCCO samples
[B. Khaykovich et. al., Phys. Rev. B 61, R9261 (2000)], we present a simple
macroscopic model describing effects of inhomogeneous current distribution and
shear in a layered superconductor. Parameters of the model are deduced from a
microscopic calculation. Our model accounts for the strong current
non-linearities and the re-entrant temperature dependence observed in the
experiment.Comment: 11 pages, 7 figures, submitted to Phys. Rev.
Microscopic derivation of Ginzburg-Landau equations for coexistent states of superconductivity and magnetism
Ginzburg-Landau (GL) equations for the coexistent states of superconductivity
and magnetism are derived microscopically from the extended Hubbard model with
on-site repulsive and nearest-neighbor attractive interactions. In the derived
GL free energy a cubic term that couples the spin-singlet and spin-triplet
components of superconducting order parameters (SCOP) with magnetization
exists. This term gives rise to a spin-triplet SCOP near the interface between
a spin-singlet superconductor and a ferromagnet, consistent with previous
theoretical studies based on the Bogoliubov de Gennes method and the
quasiclassical Green's function theory. In coexistent states of singlet
superconductivity and antiferromagnetism it leads to the occurrence of
pi-triplet SCOPs.Comment: 18 page
The 74MHz System on the Very Large Array
The Naval Research Laboratory and the National Radio Astronomy Observatory
completed implementation of a low frequency capability on the VLA at 73.8 MHz
in 1998. This frequency band offers unprecedented sensitivity (~25 mJy/beam)
and resolution (~25 arcsec) for low-frequency observations. We review the
hardware, the calibration and imaging strategies, comparing them to those at
higher frequencies, including aspects of interference excision and wide-field
imaging. Ionospheric phase fluctuations pose the major difficulty in
calibrating the array. Over restricted fields of view or at times of extremely
quiescent ionospheric ``weather'', an angle-invariant calibration strategy can
be used. In this approach a single phase correction is devised for each
antenna, typically via self-calibration. Over larger fields of view or at times
of more normal ionospheric ``weather'' when the ionospheric isoplanatic patch
size is smaller than the field of view, we adopt a field-based strategy in
which the phase correction depends upon location within the field of view. This
second calibration strategy was implemented by modeling the ionosphere above
the array using Zernike polynomials. Images of 3C sources of moderate strength
are provided as examples of routine, angle-invariant calibration and imaging.
Flux density measurements indicate that the 74 MHz flux scale at the VLA is
stable to a few percent, and tied to the Baars et al. value of Cygnus A at the
5 percent level. We also present an example of a wide-field image, devoid of
bright objects and containing hundreds of weaker sources, constructed from the
field-based calibration. We close with a summary of lessons the 74 MHz system
offers as a model for new and developing low-frequency telescopes. (Abridged)Comment: 73 pages, 46 jpeg figures, to appear in ApJ
Prognostic value of estimated glomerular filtration rate in hospitalised older patients (over 65) with COVID-19 : a multicentre, European, observational cohort study
Acknowledgements: COPE Team Members (collaborators). Funding: No funding declared for this study. The Study was sponsored by Cardiff University who had no role on the study design, analysis or interpretation of the findings. BC is partially supported by the NIHR Maudsley Biomedical Research Centre at South London Maudsley NHS Foundation Trust, and King's College London. EAR received the Gwyn Seymour Scholarship from the Department of Medicine for the Elderly, NHS Grampian, as part of the Aberdeen Summer Research Scholarship Scheme, Aberdeen Clinical Academic Training Programme, University of Aberdeen.Peer reviewedPublisher PD
On the Meissner Effect of the Odd-Frequency Superconductivity with Critical Spin Fluctuations: Possibility of Zero Field FFLO pairing
We investigate the influence of critical spin fluctuations on electromagnetic
responses in the odd-frequency superconductivity. It is shown that the Meissner
kernel of the odd-frequency superconductivity is strongly reduced by the
critical spin fluctuation or the massless spin wave mode in the
antiferromagnetic phase. These results imply that the superfluid density is
reduced, and the London penetration depth is lengthened for the odd-frequency
pairing. It is also shown that the zero field Flude-Ferrell-Larkin-Ovchinnikov
pairing is spontaneously realized both for even- and odd-frequency in the case
of sufficiently strong coupling with low lying spin-modes.Comment: 10 pages, 7 figure
Acute hepatic failure and multi-system organ failure secondary to replacement of the liver with metastatic melanoma
BACKGROUND: Metastatic malignant melanoma to the liver resulting in fulminant hepatic failure is a rare occurrence. CASE PRESENTATION: A 46 year old man presented to hospital with massive hepatomegaly, elevated liver enzymes and increased lactate three weeks following resection of a malignant melanoma from his shoulder (Clark level 5). Initially stable, he decompensated 24 to 48 hours subsequent to presentation with respiratory failure requiring mechanical ventilation, distributive shock requiring high dose vasopressor infusion, coagulopathy refractory to plasma infusion, progressive rise in liver enzymes and severe metabolic abnormalities including hyperkalemia, acidosis, hyperphosphatemia, hyperuricemia and hypocalcemia. Refractory to aggressive physiologic support he received palliation. Autopsy revealed >80% liver infiltration by metastatic malignant melanoma. CONCLUSION: We report a case of fulminant hepatic failure secondary to metastatic malignant melanoma infiltration of the liver
Nosocomial COVID-19 infection : examining the risk of mortality. The COPE-Nosocomial Study (COVID in Older PEople)
In the United Kingdom, authority to conduct the study was granted by the Health Research Authority (20/HRA/1898), and in Italy by the Ethics Committee of Policlinico Hospital Modena (Reference 369/2020/OSS/AOUMO). Cardiff University was the study sponsor.Peer reviewedPostprin
Theory of Fulde-Ferrell-Larkin-Ovchinnikov state of superconductors with and without inversion symmetry: Hubbard model approach
We study Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state of superconductors
with and without inversion symmetry based on the Hubbard model on the square
lattice near half-filling, using the random phase approximation. We show that
center of mass momentum tends to be parallel to - or y-axis in the
presence of inversion symmetry, while vector is likely to be perpendicular
to the magnetic field in the absence of inversion symmetry. We also clarify
that -wave pairing is favored and the hetero spin triplet -wave state
is present in the FFLO state unlike state in the superconductors only with the
Rashba type spin-orbit coupling (RSOC) originating from the broken inversion
symmetry. The triplet -wave state is enhanced by magnetic field and the
RSOC. This stems from the reduction of the spin susceptibilities by the
magnetic field and the RSOC.Comment: 9 pages, 15 figures, 1 tabl
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