Masses and ages of delta scuti stars in eclipsing binary systems

By using data mainly from Frolovet al. (1982) for four Delta Scuti stars in eclipsing binary systems, AB Cas, Y Cam, RS Cha, and AI Hya, their physical parameters, distances, and radial pulsation modes are determined. The evolutionary track systems of Iben (1967), Paczyski (1970), and Maeder and Meynet (1988) are interpolated, in order to estimate evolutionary massesM _eand agest of these variables. Their pulsation massesM _Qare estimated from the fitting formulae of Faulkner (1977) and Fitch (1981). Our estimates of evolutionary massesM _eand pulsation massesM _Qare close to the massesM determined by Frolovet al. (1982) from the star binarity. The only exception is AB Cas, for which there is no agreement between certain star parameters.Another, independent approach is also applied to the stars RS Cha and AI Hya: by using their photometric indicesb — y andc ₁ from the catalogue of López de Cocaet al. (1990) and appropriate photometric calibrations, other sets of physical parameters, distances, modes, ages, evolutionary and pulsation masses of both variables are obtained.     

On the Circular Polarization of Pulsar Radiation

We consider the polarization behaviour of radio waves propagating through an ultrarelativistic highly magnetized electron-positron plasma in a pulsar magnetosphere. The rotation of magnetosphere gives rise to the wave mode coupling in the polarization-limiting region. The process is shown to cause considerable circular polarization in the linearly polarized normal waves. Thus, the circular polarization observed for a number of pulsars, despite the linear polarization of the emitted normal waves, can be attributed to the limiting-polarization effect. This revised version was published online in August 2006 with corrections to the Cover Date.     

Magnetisation of titanomagnetites from Bulgarian basalts

A number of basalt samples containing titanomagnetites, with varying degrees and modes of oxidation, have been collected from 13 sites in northern Bulgaria, the degree of oxidation being determined from Curie point and lattice parameter determination. The stability of natural remanent magnetization and artificially induced thermoremanences (TRM) has been studied in an attempt to determine whether the oxidized rocks carry a TRM inherited from their original, unoxidized state. From the samples studied, it appears that the intensity and direction of the original TRM's are retained, but that there is some loss in stability.     

The provenance of terrigenous rocks of the basal horizons of the Uralides of the Baidarata Allochthon (Polar Urals) according to the U–Pb isotope age of detrital zircons

The U–Pb (LA–ICP–MS) age of detrital zircons from the Upper Cambrian–Lower Ordovician terrigenous rocks of the Baidarata Allochthon, which is located in the northern part of the Polar Urals, is determined. The analysis of the youngest zircon population indicates a broad occurrence of the Uralides in this area rather than Pre-Uralides, as was considered previously. The Bedamel island-arc rocks (rather than Timan orogen) were probably the major provenance for the studied sequences. The results of statistical processing of the U–Pb ages of zircons from coeval rocks of Arctic regions suggest similar provenances for the Baidarata Allochthon and Novaya Zemlya and Severnaya Zemlya archipelagoes.     

Water Pollution by Heavy Metals and Oil Products in Uglovoi Bay in February 2010–2016

Water Resources - Water pollution by heavy metals in Uglovoi Bay in 2015–2016 was analyzed. The concentrations of Mn, Fe, Cu, Ni, Hg, As, Pb, Cd, and oil products were found to exceed the...     

Neoproterozoic riftogenic subalkali basites of the Central Urals: Geochemical specifics of clinopyroxene

Trace-element distribution in clinopyroxenes of different generations was used to decipher the intricate melt fractionation history of the trachybasalts, trachyandesites, and gabbroids from different rift-related magmatic complexes, which were formed during evolution of the Neoproterozoic passive margin of the East European craton (western slope of the Central Urals). It was established that chromian and high-magnesian cores of the early Cpx phenocrysts in the trachybasalts are not xenogenic, but represent relict minerals that were formed at the early stage of fractionation of a high-Mg melt. The fact that the trachybasalts and trachybasaltic andesites contain high-Mg Cpx with trace-element patterns similar in shape and element abundance indicates their formation via differentiation of a common melt. However, their subsequent evolution was different: trachybasaltic andesites were subjected to significant crustal contamination, which was recorded in composition of late Cpx. All subalkali basites were presumably formed from comparatively deepseated melts, because, according to thermodynamic calculations, early cores in the gabbroids crystallized at temperature more than 1200°C and pressure between 10 and 14–15 kbar, i.e., at depths of approximately 35–50 km. Some differences observed between trace-element composition of Cpx from the studied subalkali basatoids and gabbroids are inconsistent with their derivation from a common source, but similarity of their Cpx in many characteristics undoubtedly indicates close depths and compositions of their sources. Geochemical peculiarities of Cpx in the Neoproterozoic rift rocks from the western slope of the Central Urals testify that they were derived from melts formed by relatively low degree partial melting with garnet in residue. The geochemical specifics of clinopyroxenes from the Neoproterozoic riftogenic subalkali basites of the Central Urals and basaltoids from the Paleozoic Tagil structure of the same region showed that this island-arc system reflects the composition of melt source and its reworking by mantle fluids, which were different in the course of plume-lithosphere interaction and suprasubduction processes.     

Studying the response of Lake Ladoga ecosystem to a decrease in phosphorus load

A study of the transformation of Lake Ladoga ecosystem in 1996–2005 shows that a decrease in the phosphorus load after 1995 has not cause a decrease in lake ecosystem productivity. Mathematical modeling provided an explanation of the observed phenomenon, thus justifying limnologists’ hypothesis that phosphorus turnover within a water body accelerates with increasing abundance of bacterioplankton and aquatic fungi. Computational experiments have shown that the additional amount of phosphorus that is required for maintaining phytoplankton productivity is additionally released by destructors (bacterioplankton and aquatic fungi) from detritus and organic matter dissolved in water.     

Redistribution of radionuclides between a microbial mat and a carbonate body at the Garga hot spring (Baikal Rift Zone)

The features of present deposits that form in the vicinity of hot springs can provide clues to the parameters of paleowaters in places of past hydrothermal activity marked by remnant carbonate and/or siliceous sinter. We investigated a large carbonate body at the Garga hot spring developing in the Baikal zone of nitric hydrotherms in the Barguzin Rift Zone valley. The main focus was on the structure of the carbonate mound, as well as on the partitioning of radioactive elements between the cyanobacterial mat and the inorganic component of the body (the issue that has never been explored before). The cyanobacterial community of the Garga spring is an active biosorbent of ²²⁶Ra, ²²⁸Ra, ²¹⁰Pb. The radionuclides accumulated by biosorption become preserved in minerals that form within the bacterial community. The reported data of mineral formation in the cyanobacterial mat along with the mineralogy and structure of the carbonate mound of the Garga spring have implications for the complex history of the Garga body. It has been produced jointly by precipitation from the venting thermal water (opal-calcite-fluorite-barite-celestine assemblage) and microbial metabolic activity (coarse calcite and thin black encrustation rich in Mn minerals).     

MORPHOMETRIC MAPS OF GLACIAL SURFACE TOPOGRAPHY

Several procedures for mapping the topography of the surface of an alpine glacier are described: slope angle mapping, mapping of dissection depths, trend surface analysis, and the mapping of residuals. Methodological problems addressed include determination of class intervals for mapping, data transformation techniques, and an entire range of issues connected with proper sampling methods. The purpose is to demonstrate how the mapping of multiple indicators of ice-surface relief increases the flexibility of cartographic methods for identifying underlying geomorphological processes. Translated from: Vestnik Leningradskogo Universiteta, 1984, No. 6, pp. 43-48.