The problem of the high mass of the hot component in the recurrent nova T Coronae Borealis solved after 38 years

In this paper, we present long-term spectroscopic observations of the recurrent nova (RN) T CrB obtained between the years 1985 and 1996 using 1.02 m and 2.34 m telescopes of the Vainu Bappu Observatory in India and the long-term photoelectric photometry of the object obtained mainly at the Skalnaté Pleso Observatory and at the Hlohovec Observatory in Slovakia. On the basis of our results, we have returned to the re-analysis of the old radial-velocity measurements published by Kraft (1958). The results obtained solve unambiguously the problem of the apparently too high mass of the hot component of T CrB, unacceptable if it has to be a white dwarf (WD), as several independent lines of evidence suggest

Uporaba usporednog računalnog sustava za modeliranje geoloških fenomena u sustavu zemljopisnih informacija (GIS)

Geographical data processing using Geographical Information Systems on single processor computer is going to be very difficult in consideration of constantly growing amount of data. In the recent years there is a trend of operation of those systems on parallel computers, which brings an effect mainly in the area of their performance. This article deals with possibilities of shortening of time demanded for mathematically exacting process of both analysis and visualization of variety of geographical data using parallel architectures. It focuses on some methods of geographical data processing as well as on types of parallel computing systems, together with description of their practical application to the environment of Geographical Information Systems.Obrada zemljopisnih podataka uporabom Geographical Information System (GIS) na jedno-procesnom kompjutoru bit će vrlo teška ako se uzme u obzir stalni porast količine podataka. Zadnjih godina postoji tendencija rada tih sustava na usporednim računalima, a to ima utjecaja uglavnom na područje njihovih performansi. Ovaj članak se bavi mogućnostima skraćivanja vremena potrebnog za komplicirane (exacting) matematičke operacije i vizualizacije mnoštva zemljopisnih podataka uporabom usporednih arhitektura. Usredotočuje se na neke metode obrade zemljopisnih podataka kao i na tipove usporednih računalnih sustava, zajedno s opisom njihove praktične primjene na okoliš Grographical Information Systems

Protracted shearing at mid‐crustal conditions during large‐scale thrusting in the Scandinavian Caledonides

During continental collision, large tracts of crust are mobilised along major shear zones. The metamorphic conditions at which these zones operate, the duration of thrusting, and the deformation processes that facilitated hundreds of km of tectonic transport are still unclear. In the Scandinavian Caledonides, the Lower Seve Nappe displays a main mylonitic foliation with thickness of ~1 km. This foliation is overprinted by a brittle‐to‐ductile deformation pattern localized in C and C’‐type shear bands proximal to the tectonic contact with the underlying Särv Nappe. Thermobarometry of amphibolites and micaschists suggest a first high‐pressure stage at 400‐500°C and 1‐1.3 GPa recorded in mineral relics. The main mylonitic foliation developed under epidote amphibolite facies conditions along the retrograde path from 600°C and 1 GPa to 500°C and 0.5 GPa. Age dating of synkinematic titanite grains in the amphibolites indicates that this mylonitic fabric formed at around 417 ± 9 Ma, but older ages spanning 460‐430 Ma could represent earlier stages of mylonitization. The shear bands developed at lower metamorphic conditions of 300‐400°C and ~0.3 GPa. In the micaschists, the recrystallized grain size of quartz decreases towards the shear bands. Monomineralic quartz layers are eventually dismembered to form polyphase aggregates deforming by dominant grain size sensitive creep accompanied by slip in muscovite and chlorite. Plagioclase zoning truncations suggest that the shear bands originated by fracturing followed by ductile deformation. The results suggest protracted and long‐lasting shearing under amphibolite to greenschist facies conditions during the juxtaposition, stacking and exhumation of the Lower Seve Nappe

Impact of Polychlorinated Biphenyls Contamination on Estrogenic Activity in Human Male Serum

Polychlorinated biphenyls (PCBs) are thought to cause numerous adverse health effects, but their impact on estrogen signaling is still not fully understood. In the present study, we used the ER-CALUX bioassay to determine estrogenic/antiestrogenic activities of the prevalent PCB congeners and PCB mixtures isolated from human male serum. The samples were collected from residents of an area with an extensive environmental contamination from a former PCB production site as well as from a neighboring background region in eastern Slovakia. We found that the lower-chlorinated PCBs were estrogenic, whereas the prevalent higher-chlorinated PCB congeners 138, 153, 170, 180, 187, 194, 199, and 203, as well as major PCB metabolites, behaved as anti-estrogens. Coplanar PCBs had no direct effect on estrogen receptor (ER) activation in this in vitro model. In human male serum samples, high levels of PCBs were associated with a decreased ER-mediated activity and an increased dioxin-like activity, as determined by the DR-CALUX assay. 17β-Estradiol (E(2)) was responsible for a major part of estrogenic activity identified in total serum extracts. Significant negative correlations were found between dioxin-like activity, as well as mRNA levels of cytochromes P450 1A1 and 1B1 in lymphocytes, and total estrogenic activity. For sample fractions containing only persistent organic pollutants (POPs), the increased frequency of anti-estrogenic samples was associated with a higher sum of PCBs. This suggests that the prevalent non-dioxin-like PCBs were responsible for the weak antiestrogenic activity of some POPs fractions. Our data also suggest that it might be important to pay attention to direct effects of PCBs on steroid hormone levels in heavily exposed subjects

More on the pulsation period of the cool component in the symbiotic binary AG Dra

We have combined recent radial velocity measurements of Fekel et al. ([CITE]) with previously studied older ones, to test for the continued presence of the second period, found by Gális et al. ([CITE]), which could be due to pulsations of the cool component of the AG Dra binary system. Fekel's data, even taken by themselves, also marginally suggest the presence of variations near the previously found second period. The period is in any case clearly seen, when all radial velocity measurements are combined

Photometry of the dust nova V705 Cassiopeiae

We present the results of our UBV photoelectric photometry of V705 Cas (Nova Cassiopeiae 1993) obtained at the Skalnaté Pleso, Stará Lesná, Hlohovec and Brno Observatories. The observations cover the light curve development of this nova over its stages of dust formation and disappearance of the envelope. The results of the light curve analysis are presented. We have also used the visual brightness estimates of V705 Cas by the members of the VSNET network as an auxiliary data set in order to determine the nova's brightness behaviour as accurately as possible. The basic parameters of the brightness decline of the nova $t_{2,B}= 40$ d, $t_{2,V} =$ 33 d, $t_{3,B} =$ 63 d, $t_{3,V} =$ 61 d, with the accuracy not worse than one day, were obtained on the basis of our light curves. The relevant value of $M_{B}= (-7.27 \pm{0.3})$ mag and the value $M_{V}= (-7.32\pm{0.22})$ mag in the maximum of brightness were derived. The corresponding value of the mass of the white dwarf component of the presumable underlying nova binary is $M_{\rm WD}= (0.79\pm{0.06})$ $M_{\odot}$. The colour excess at brightness maximum is $E_{B{-}V}= 0.56$ mag and the corresponding value of the distance $r= (1.67\pm{0.34})$ kpc. This value of the distance is very probably underestimated due to the strong extinction by the dust envelope of the nova. The general problem of the use of statistical calibrations as well as that of the distance determination for dust novae is discussed

The orbital modulation of the X-ray binary V Sagittae in the high and low states

Our analysis of the orbital modulation of V Sge, carried out in the intensity scale instead of the previously used magnitude scale, revealed that the full amplitude of the modulation remains almost constant as the intensity of the system rises from the low to the high state. The primary minimum remains very similar, as regards both its depth and width. The secondary minimum tends to slightly lag behind phase 0.5. The depth of the secondary minimum is subjected to the largest changes; it becomes almost as deep as the primary minimum during the high state while it is significantly more shallow than the primary one in the low state