46 research outputs found
Pressure-dependence of electron-phonon coupling and the superconducting phase in hcp Fe - a linear response study
A recent experiment by Shimizu et al. has provided evidence of a
superconducting phase in hcp Fe under pressure. To study the
pressure-dependence of this superconducting phase we have calculated the phonon
frequencies and the electron-phonon coupling in hcp Fe as a function of the
lattice parameter, using the linear response (LR) scheme and the full potential
linear muffin-tin orbital (FP-LMTO) method. Calculated phonon spectra and the
Eliashberg functions indicate that conventional s-wave
electron-phonon coupling can definitely account for the appearance of the
superconducting phase in hcp Fe. However, the observed change in the transition
temperature with increasing pressure is far too rapid compared with the
calculated results. For comparison with the linear response results, we have
computed the electron-phonon coupling also by using the rigid muffin-tin (RMT)
approximation. From both the LR and the RMT results it appears that
electron-phonon interaction alone cannot explain the small range of volume over
which superconductivity is observed. It is shown that
ferromagnetic/antiferromagnetic spin fluctuations as well as scattering from
magnetic impurities (spin-ordered clusters) can account for the observed values
of the transition temperatures but cannot substantially improve the agreeemnt
between the calculated and observed presure/volume range of the superconducting
phase. A simplified treatment of p-wave pairing leads to extremely small ( K) transition temperatures. Thus our calculations seem to rule out
both - and - wave superconductivity in hcp Fe.Comment: 12 pages, submitted to PR
Extended Theories of Gravity and their Cosmological and Astrophysical Applications
We review Extended Theories of Gravity in metric and Palatini formalism
pointing out their cosmological and astrophysical application. The aim is to
propose an alternative approach to solve the puzzles connected to dark
components.Comment: 44 pages, 11 figure
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Regional variations in myosin heavy chain concentration after healing of experimental myocardial infarction in cats
Densitometric scanning of SDS-polyacrylamide gels was used to measure myosin heavy chain concentration in left ventricular specimens obtained from cat heart 3 to 12 months after healing of small experimental myocardial infarctions. The study was designed to test the hypothesis that myosin concentration varies as a function of anatomic proximity to the infarct scar. Myosin heavy chain concentration was
elevated in non-scarred areas adjacent to a healed infarct and normal in areas remote from the scar. The scar itself had reduced concentrations, reflecting the loss of muscle mass in this area. The increased myosin heavy chain concentration in regions adjacent to the scar may be an attempt to regulate or compensate for the decrease in mechanical function of the scarred area