Species Distribution Patterns in Subgenus Cuspidata (Genus Sphagnum L.) on the East European Plain and Eastern Fennoscandia

The geographic range of 13 species from the subgenus Cuspidata in the East European Plain and Eastern Fennoscandia has been studied. Model maps for each species occurrence were constructed using geostatistics techniques (kriging method). Continuous coverages of 23 climatic factors were used in analysis also. We used dataset that proposed by authors of program WORLDCLIM. To learn how corresponding values of climatic factors and species occurrence correlation and cluster analysis were conducted. It was found that 7 of 13 species are widespread on the East European Plain and Eastern Fennoscandia, and 6 species have the restricted ranges. Values of occurrence of all species (except Sphagnum lenense) have a strong correlation with moisture factors (relative air humidity and sum of precipitation) in summer-autumn period. Such preferences allow them to grow successfully in Subarctic and Baltic regions, where high climatic humidity is observed. Restricted species are concentrated around the Baltic Sea and zones of the highest occurrence of widespread species are located at the same region. All species can be divided into four clusters according to its climatic preferences. Distribution of such species as S. obtusum seems to be strongly associated with two tongues of the Last Glacier, and this species seems to be a glacial relic

The zoo of isolated neutron stars

In this brief review I summarize our basic knowledge about different types of isolated neutron stars. I discuss radio pulsars, central compact objects in supernova remnants, magnetars, near-by cooling neutron stars (aka the Magnificent seven), and sources of fast radio bursts. Several scenarios of magneto-rotational evolution are presented. Recent observational data, in the first place -- discovery of long period radio pulsar, require non-trivial evolution of magnetics fields or/and spin periods of neutron stars. In some detail I discuss different models of magnetic field decay and interaction of young neutron stars with fallback matter.Comment: 25 pages, accepted for publication in Universe, special issue "Selected Papers from the 2nd International Electronic Conference on Universe (ECU 2023)

Strange quark stars in binaries: formation rates, mergers and explosive phenomena

The existence of strange quark stars has been proposed many years ago. More recently, the possible co-existence of a first family composed of "normal" neutron stars with a second family of strange quark stars has been proposed as a solution of problems related to the maximum mass and to the minimal radius of these compact stellar objects. In this paper we study the mass distribution of compact objects formed in binary systems and the relative fractions of quark and neutron stars in different subpopulations. We incorporate the strange quark star formation model provided by the two-families scenario and we perform a large-scale population synthesis study in order to obtain the population characteristics. In our model, below a critical gravitational mass $M_\mathrm{max}^H- \Delta M$ only normal (hadron) neutron stars exist. Then in the mass range $(M_\mathrm{max}^H- \Delta M) \leqslant M \leqslant M_\mathrm{max}^H$ strange quark stars and neutron stars coexist. Finally, above $M_\mathrm{max}^H$ all compact objects are strange quark stars. We argue that $M_\mathrm{max}^H$ is in the range $\sim 1.5-1.6 M_\odot$. According to our results, the main channel for strange quark star formation in binary systems is accretion from a secondary companion on a neutron star.This opens the possibility of having explosive GRB-like phenomena not related to supernovae and not due to the merger of two neutron stars. The enhancement in the number of compact objects in the co-existence mass range $(M_\mathrm{max}^H- \Delta M) \leqslant M \leqslant M_\mathrm{max}^H$ is not very pronounced. The number of double strange quark star's systems is rather small with only a tiny fraction which merge within a Hubble time. This drastically limits the flux of strangelets produced by the merger, which turns out to be compatible with all limits stemming from Earth and lunar experiments.Comment: 11 pages, 10 figures, minor typos corrected, ApJ, 846, 16

Mirrorless Negative-index Parametric Micro-oscillator

The feasibility and extraordinary properties of mirrorless parametric oscillations in strongly absorbing negative-index metamaterials are shown. They stem from the backwardness of electromagnetic waves inherent to this type of metamaterials.Comment: 4 pages, 2 figure

Two-section fiber optic Raman polarizer

We report on a theoretical study of polarization impairments in periodically spun fiber Raman amplifiers. Based on the Stochastic Generator approach we have derived averaged equations to calculate polarization dependent gain and mean-square gain fluctuations. We show that periodically spun fiber can work as a Raman polarizer but it suffers from increased polarization dependent gain and gain fluctuations. Unlike this, application of a depolarizer can result in suppression of polarization dependent gain and gain fluctuations. We demonstrate that it is possible to design a new fiber Raman polarizer by combining a short fiber without spin and properly chosen parameters and a long periodically spun fiber. This polarizer provides almost the same polarization pulling for all input signal states of polarization and so has very small polarization dependent gain