Stanislav Hledík

Evolution of Kerr superspinars due to accretion counterrotating thin discs

String theory predicts the existence of extremely compact objects spinning faster than Kerr black holes. The spacetime exterior to such superspinars is described by Kerr naked singularity geometry breaking the black-hole limit on the internal angular momentum. We demonstrate that the conversion of Kerr superspinars into a near-extreme black hole due to an accretion counterrotating Keplerian disc is much more effective in comparison with the case of a corotating one since both the accreted rest mass necessary for conversion and the evolution time of conversion are by orders smaller for counterrotating discs. The conversion time of Kerr superspinars is given for several accretion regimes, and it is shown that the self-regulated accretion flow implies fastest evolution to the black-hole state. In the final stages of the conversion, Kerr superspinars can serve as very efficient particle accelerators in the region where the black-hole horizon forms.

Gravitational excitation of high frequency QPOs (Research Note)

We discuss the possibility that high-frequency QPOs in neutron-star binary systems may result from forced resonant oscillations of matter in the innermost parts of the accretion disc, excited by gravitational perturbations coming from asymmetries of the neutron star or from the companion star. We find that neutron-star asymmetries could, in principle, be effective for inducing both radial and vertical oscillations of relevant amplitude while the binary companion might possibly produce significant radial oscillations but not vertical ones. Misaligned neutron-star quadrupole moments of a size advocated elsewhere for explaining limiting neutron star periods could be large enough also for the present purpose.

Objective evaluation of the effect of autologous platelet concentrate on post-operative scarring in deep burns.

INTRODUCTION The healing of grafted areas after surgical treatment of deep burns frequently generates mutilating scars, and rises the risk of subsequent scar hypertrophy. Scar assessment based on clinical evaluation is inherently subjective, which stimulates search for objective means of evaluation. OBJECTIVE The aim of this study was to objectively evaluate the effect of using autologous platelet concentrate (APC) in combination with split thickness skin grafting (STSG) on scarring processes following surgery of deep burns as compared with application of STSG alone. METHOD Selected viscoelastic properties of 38 scars on 23 patients in total were examined using the Cutometer MPA 580 under controlled conditions for long-term outcomes 1, 3, 6 and 12 months after surgery following deep burns. RESULTS The findings of this study suggest that the STSG+APC combination reduces the time of scar viscoelastic properties recovery as compared with application of STSG alone. This was statistically significant for viscoelastic parameters R2 and Q1. CONCLUSION APC has been advocated to enhance scarring after surgery of deep dermal and full thickness burns. We objectively demonstrated that the viscoelastic properties of scars treated with STSG+APC combination return more rapidly to the plateau state than areas treated with STSG only.

General relativistic polytropes with a repulsive cosmological constant

Spherically symmetric equilibrium configurations of perfect fluid obeying a polytropic equation of state are studied in spacetimes with a repulsive cosmological constant. The configurations are specified in terms of three parameters\char22{}the polytropic index

Extreme gravitational lensing in vicinity of Schwarzschild-de Sitter black holes

n

The time factor in the LDI (Laser Doppler Imaging) diagnosis of burns

, the ratio of central pressure and central energy density of matter

Photon capture cones and embedding diagrams of the Ernst spacetime

\ensuremath{\sigma}

Optical reference geometry of Kerr-Newman spacetimes

, and the ratio of energy density of vacuum and central density of matter

TRAPPING OF NEUTRINOS IN EXTREMELY COMPACT STARS

\ensuremath{\lambda}

A VIRTUAL TRIP TO THE SCHWARZSCHILD-DE SITTER BLACK HOLE

. The static equilibrium configurations are determined by two coupled first-order nonlinear differential equations that are solved by numerical methods with the exception of polytropes with