The thermal history of the intergalactic medium at 3.9≤z≤4.33.9 \leq z \leq 4.3

A new determination of the temperature of the intergalactic medium over $3.9 \leq z \leq 4.3$ is presented. We applied the curvature method on a sample of 10 high resolution quasar spectra from the Ultraviolet and Visual Echelle Spectrograph on the VLT/ESO. We measured the temperature at mean density by determining the temperature at the characteristic overdensity, which is tight function of the absolute curvature irrespective of $\gamma$. Under the assumption of fiducial value of $\gamma = 1.4$, we determined the values of temperatures at mean density $T_{0} = 7893^{+1417}_{-1226}$ K and $T_{0} = 8153^{+1224}_{-993}$ K for redshift range of $3.9 \leq z \leq 4.1$ and $4.1 \leq z \leq 4.3$, respectively. Even though the results show no strong temperature evolution over the studied redshift range, our measurements are consistent with an intergalactic medium thermal history that includes a contribution from He II reionization.Comment: Accepted for publication in PASA, 9 pages, 8 figure

Recent outburst activity of the symbiotic binary AG Draconis

The symbiotic binary AG Dra regularly undergoes quiescent and active stages which consist of several outbursts repeating with about 360d interval. The recent outburst activity of AG Dra started by the minor outburst in the late spring of 2015 and was definitely confirmed by the outbursts in April 2016 and May 2017. In the presented work, the photometric and spectroscopic behaviour of the recent outburst activity of AG Dra is presented in detail. Moreover, the temperature of the white dwarf in AG Dra is studied based on the behaviour of the prominent emission lines. We show that a disentanglement of particular effects in the observed changes of the emission lines is crucial to investigate the intrinsic white dwarf temperature variations related to outburst activity of this strongly interacting binary. We also report the effects of the low excitation lines orbital variations and of the H$_{\beta}$ absorption component on their equivalent widths as well as consequences of the approximations used in our previous works.Comment: 16 pages, 4 figures, Proceedings of The Golden Age of Cataclysmic Variables and Related Objects IV, 11-16 September 2017. Palermo, Ital

Influence of combination of simple beam loading on the safety with respect to the limit state of elasticity

Táto bakalárska práca sa zaoberá vyhodnocovaním vplyvu kombinácie prostého namáhania pre prúty s rôznymi typmi priečnych prierezov z hľadiska medzného stavu pružnosti. V prvej časti práce sú zhrnuté teoretické poznatky o prostom a kombinovanom namáhaní, medznom stave pružnosti a metóde konečných prvkov. Následne je pre prúty rôznych priečnych prierezov vyhodnotená bezpečnosť k medznému stavu pružnosti analytickým výpočtom a numerickým výpočtom pomocou metódy konečných prvkov.This bachelor thesis deals with the evaluation of the influence of the combined loading for beams with different types of cross-sections in terms of the limit state of elasticity. The first part of the thesis summarizes the theoretical knowledge about simple and combined loading, the limit state of elasticity and the finite element method. Then, the safety of the limit state of elasticity is evaluated for the beams of different cross-sections by analytical calculations and numerical calculations using the finite element method.

Cataclysmic Variables — X-rays and Optical Activity in V1223 Sgr and V709 Cas

Intermediate polars are a major fraction of all cataclysmic variables detected by INTEGRAL in hard X-ray. These objects have recently been proposed to be the dominant X-ray source population detected near the Galactic centre, and they also contribute significantly to X-ray diffuse Galactic ridge emission. Nevertheless, only 25% of all known intermediate polars have been detected in hard X-ray. This fact can be related to the activity state of these close interacting binaries.A multi-frequency (from optical to X-ray) investigation of intermediate polars is essential for understanding the physical mechanisms responsible for the observed activity of these objects