Stars with discrepant v sin i as derived from Ca II 3933 and Mg II 4481 Å lines. I. Composite-spectrum star HD 2913

Axial rotation of a star plays an important role in its evolution, physical conditions in its atmosphere and the shape of its spectrum. Methods of determining of v sin i are based on comparison of the observed profiles of spectral lines with the theoretical ones. Their accuracy depends on the type and quality of spectrograms, as well as on the algorithms used. A frequently used method is a simple comparison of one line, e.g. the Ca ii at 3933 Å or Mg ii at 4481 Å. This, however, may result in a false value of v sin i in case when low-dispersion spectra are used. We investigate the spectra of stars with a significant discrepancy of their rotational velocities introduced in various sources, and analyze the corresponding spectral region from the point of view of possible admixed features, which may mask the true line profiles. We use CCD spectra of the stars having this discrepancy, to compare with theoretical spectra. We also studied photographic spectra, obtained during the 1970s and 1980s. In this work we studied the spectra of the binary HD 2913A, and identified the spectrum of its weaker component designated as “Ab”. We estimated the effective temperature, surface gravity and projected rotational velocity of the weaker component that classify it as an early F-type Main Sequence star. The discrepancy between the values of v sin i derived from the two lines of calcium and magnesium is explained as a consequence of superposition of the pair’s spectra. The cooler component contributes by a strong Ca ii-K line, and thus significantly broadens the observed line profile.     

Kinematics of Interacting ICMEs and Related Forbush Decrease: Case Study

We study heliospheric propagation and some space weather aspects of three Earth-directed interplanetary coronal mass ejections (ICMEs), successively launched from the active region AR 11158 in the period 13?–?15 February 2011. From the analysis of the ICME kinematics, morphological evolution, and in situ observations, we infer that the three ICMEs interacted on their way to Earth, arriving together at 1 AU as a single interplanetary disturbance. Detailed analysis of the in situ data reveals complex internal structure of the disturbance, where signatures of the three initially independent ICMEs could be recognized. The analysis also reveals compression and heating of the middle ICME, as well as ongoing magnetic reconnection between the leading and the middle ICME. We present evidence showing that the propagation of these two, initially slower ICMEs, was boosted by the fastest, third ICME. Finally, we employ the ground-based cosmic ray observations, to show that this complex disturbance produced a single cosmic ray event, i.e., a simple Forbush decrease (FD). The results presented provide a better understanding of the ICME interactions and reveal effects that should be taken into account in forecasting of the arrival of such compound structures.     

Consequences of climate change for the soil climate in Central Europe and the central plains of the United States

This study aims to evaluate soil climate quantitatively under present and projected climatic conditions across Central Europe (12.1°–18.9° E and 46.8°–51.1° N) and the U.S. Central Plains (90°–104° W and 37°–49° N), with a special focus on soil temperature, hydric regime, drought risk and potential productivity (assessed as a period suitable for crop growth). The analysis was completed for the baselines (1961–1990 for Europe and 1985–2005 for the U.S.) and time horizons of 2025, 2050 and 2100 based on the outputs of three global circulation models using two levels of climate sensitivity. The results indicate that the soil climate (soil temperature and hydric soil regimes) will change dramatically in both regions, with significant consequences for soil genesis. However, the predicted changes of the pathways are very uncertain because of the range of future climate systems predicted by climate models. Nevertheless, our findings suggest that the risk of unfavourable dry years will increase, resulting in greater risk of soil erosion and lower productivity. The projected increase in the variability of dry and wet events combined with the uncertainty (particularly in the U.S.) poses a challenge for selecting the most appropriate adaptation strategies and for setting adequate policies. The results also suggest that the soil resources are likely be under increased pressure from changes in climate.     

National minorities in the Republic of Croatia

As of 1991, in the Republic of Croatia 16 percent of the total population was made up of national minorities. A large part of this figure consists of minrity nations who are the descendants of settlers from the era of Ottoman conquest during the sixteenth and seventeenth centuries, the Austrian colonization in the eighteenth and nineteenth centuries, and partially due to inter-republic migrations during the existence of the Yugoslav state.The most numerous national minority in 1991 were the Serbs (582,000, or 12.16% of the total population). The Serbian national minority is scattered throughout the Croatian state, so that in Croatia there is no integral Serbian ethnic territory. The other national minorities in Croatia are much smaller in number (Bosnian Muslims, 43,000; Slovenes, 22,000; Hungarians, 22,000; Italians, 21,000; Czechs, 13,000; Albanians, 12,000; etc.).The conflicts provoked by Greater Serbian politics and the wartime aggression against Croatia resulted in migrations, the consequence of which is the reduction in the number of the Serbian national minority in the Republic of Croatia.     

The relevance of bisphenol A adsorption during Fenton’s oxidation

The aim of this research was to assess the efficiency of Fenton’s oxidation for degradation of endocrine disruptor bisphenol A (BPA) with emphasis on extent of accompanying adsorption. Adsorption on the waste sludge resulting from the Fenton’s oxidation could represent a significant impact on the final removal efficiency of BPA. Fenton’s oxidation was accomplished at two concentrations of BPA (0.228 and 22.8 mg L^?1); both at the selected molar ratio of reagents Fe²⁺:H₂O₂ (1:10), as a function of reaction time. The kinetics of adsorption of BPA on waste sludge was determined for the same two concentrations of BPA at two concentrations of waste sludge (0.1 and 6.0 g L^?1). In addition to changing concentrations of BPA and sludge, the adsorption process was also influenced by parameters such as temperature, pH and contact time. Adsorption isotherms were determined. Oxidation and adsorption were monitored by gas chromatography combined with mass spectrum. It has been confirmed that BPA is not completely oxidized in Fenton’s oxidation, because it is adsorbed to formed waste ferric sludge and thus necessary precautions for sludge deposition must be observed.     

Influence of crack distribution of rocks on P‐wave velocity anisotropy – a laboratory and field scale study‡

The purpose of this paper is the comparison of P‐wave velocity and velocity anisotropy, measured at different scales under laboratory and field conditions. A shallow seismic refraction survey with shot/receiver spacing of up to 10 m was carried out on a flat outcrop of lhertzolite in the southern part of the Balmuccia massif. Oriented rock samples were also obtained from the locality. The particular advantage of the laboratory method used is the possibility of measuring velocity in any direction under controlled conditions. Laboratory tests were made on spherical peridotite samples, 50 mm in diameter, by ultrasonic velocity measurements in 132 directions (meridian and parallel networks) under confining stress ranging from atmospheric to 400 MPa. The mean P‐wave velocity of the field and laboratory data differed by between 20–30%. In addition, P‐wave velocity anisotropy of 25% was detected in the field data. Whereas the anisotropy in the laboratory samples in the same orientation as the field surveys was less than 2%. This observed scaling factor is related to the different sampling sizes and the difference in frequencies of applied elastic waves. With an ultrasonic wavelength of 10 mm, laboratory samples represent a continuum. The field velocities and velocity anisotropy reflect the presence of cracks, which the laboratory rock samples do not contain. Three sub‐vertical fracture sets with differing strikes were observed in the field outcrop. Estimates of fracture stiffness from the velocity anisotropy data are consistent with other published values. These results highlight the difficulty of using laboratory velocity estimates to interpret field data.