Lithium lines in spectra of C-giants

The resonance λ 670.8 nm and subordinate λλ 812.6, 610.4, 497.2, and 460.3 nm lithium lines are investigated as the lithium abundance indicators in spectra of cool C-giants

Analysis of the spectral energy distribution of the coolest RCrB type carbon star DY Per

We analyse the spectral energy distribution of the evolved carbon giant DY Per with a spectral synthesis technique. The red giant shows the photometric features of R CrB type stars. We derive the atmospheric parameters of DY Per using three variants of molecular line lists. We estimate Teff to be in the range 2900 < Teff < 3300 K. We adopted log g = 0. The star may be metal deficient and hydrogen deficient. The maximum possible carbon abundance in the star, [C]=0.94, provides the following atmospheric parameters: Tef=3100 K, [Fe/H] = 0, log(C/O)=0.6, [N/Fe] = 0, [H/He] = 0, with Jorgensen's line lists for the molecules C2 and CN.Comment: 4 pages, 2 tables, 3 figs, accepted by Odessa asronomical observatory Publ., 200

Reactivity of a Simplest Conjugated Diolefin in Liquid-Phase Oxidation: Mechanisms and Products

Ethylene is the simplest member of olefin series, but butadiene-1,3 (BD) is the simplest conjugated diolefin. In this chapter, we describe liquid-phase oxidations of BD with an emphasis on comparison of the diolefin with monoolefins. BD interacts with oxygen to form polyperoxide, whose thermal decomposition or hydrogenation leads to the formation of 2-butene-1,4-diol, 3-butene-1,2-diol, or butanediols together with furan and acrolein. BD can be oxidized in polar solvents by radical chain route to form directly the dioxygenates. Metal catalysts are able to control the oxidation by promoting formation of 2-butene-1,4-diol, 4-hydroxybut-2-enal, and furan. PdTe/C catalyst is applied in industry to produce 2-butene-1,4-diol diacetates with selectivity of 98%. The outstanding selectivity of the catalyst is caused by combined action of components in nonradical route and esterification of final product in acetic acid. Similar reaction in methyl alcohol yields 1,4-dimethoxy-2-butene, but with lower efficiency. The nonradical mechanism is firmly established for epoxidation of BD with hydrogen peroxide catalyzed by phosphotungstates. The selectivity of BD and hydrogen peroxide conversion to 3,4-epoxy-1-butene around 100% is attained. Analysis of published information and our own studies show many similarities in oxidation of BD and light olefins, which are very useful for understanding the mechanisms

Modeling the spectrum of V4334 Sgr (Sakurai's Object)

Theoretical spectral energy distributions were computed for a grid of hydrogen-deficient and carbon-rich model atmospheres of T(eff) in the range of 5000-6250 K and log g = 1.0 - 0.0 by the technique of opacity sampling, taking into account continuous, molecular band and atomic line absorption. These energy distributions were compared with the spectrum of V4334 Sgr (Sakurai's object) of April, 1997 in the wavelength interval 300-1000 nm. We show that (1) the shape of the theoretical spectra depends strongly on T(eff) but only very weakly on the hydrogen abundance; (2) the comparison of the observed and computed spectra permits to estimate T(eff) approximately 5500 K for V4334 Sgr in April, 1997, and its interstellar reddening (plus a possible circumstellar contribution) E(B-V) approximately 0.70.Comment: 7 pages, 8 figures, LaTeX, accepted by Astronomy and Astrophysic

The data processing and decision support in healthcare systems

The article describes the characteristics of diagnostic and management tasks solved in healthcare information systems. We propose an approach based on the use of ensemble models (variant modeling) to solve problems of decision support. The variant modeling is a method that applies the set of models for solving one task. The models can have different structures and use different input features. Also, we propose the method called “Modeleteka” for structure store and automatically select models to solve tasks in healthcare information systems. This method allows append new models and train old from ensemble in the maintenance of information system

A detailed study of Lithium in 107 CHEPS dwarf stars

Reproduced with permission from Astronomy & Astrophysics, © ESO 2018.Context. We report results from lithium abundance determinations using high resolution spectral analysis of the 107 metal-rich stars from the Calan-Hertfordshire Extrasolar Planet Search programme. Aims. We aim to set out to understand the lithium distribution of the population of stars taken from this survey. Methods. The lithium abundance taking account of non-local thermodynamical equilibrium effects was determined from the fits to the Li I 6708 Å resonance doublet profiles in the observed spectra. Results. We find that a) fast rotators tend to have higher lithium abundances; b) log N(Li) is higher in more massive and hot stars; c) log N(Li) is higher in stars of lower log g; d) stars with the metallicities >0.25 dex do not show the lithium lines in their spectra; e) most of our planet hosts rotate slower; and f) a lower limit of lithium isotopic ratio is 7Li/ 6Li > 10 in the atmospheres of two stars with planets (SWP) and two non-SWP stars. Conclusions. Measurable lithium abundances were found in the atmospheres of 45 stars located at distances of 20-170 pc from the Sun, for the other 62 stars the upper limits of log N(Li) were computed. We found well defined dependences of lithium abundances on T eff, V sin i, and less pronounced for the log g. In case of V sin i we see two sequences of stars: with measurable lithium and with the upper limit of log N(Li). About 10% of our targets are known to host planets. Only two SWP have notable lithium abundances, so we found a lower proportion of stars with detectable Li among known planet hosts than among stars without planets. However, given the small sample size of our planet-host sample, our analysis does not show any statistically significant differences in the lithium abundance between SWP and stars without known planets.Peer reviewe

Nitrogen abundances in Planet-harbouring stars

We present a detailed spectroscopic analysis of nitrogen abundances in 91 solar-type stars, 66 with and 25 without known planetary mass companions. All comparison sample stars and 28 planet hosts were analysed by spectral synthesis of the near-UV NH band at 3360 \AA observed at high resolution with the VLT/UVES,while the near-IR NI 7468 \AA was measured in 31 objects. These two abundance indicators are in good agreement. We found that nitrogen abundance scales with that of iron in the metallicity range -0.6 <[Fe/H]< +0.4 with the slope 1.08 \pm 0.05. Our results show that the bulk of nitrogen production at high metallicities was coupled with iron. We found that the nitrogen abundance distribution in stars with exoplanets is the high [Fe/H] extension of the curve traced by the comparison sample of stars with no known planets. A comparison of our nitrogen abundances with those available in the literature shows a good agreement.Comment: 15 pages, 7 figures, Accepted for publication in A&

Galactic Evolution of Nitrogen

We present detailed spectroscopic analysis of nitrogen abundances in 31 unevolved metal-poor stars analysed by spectral synthesis of the near-UV NH band at 3360 A observed at high resolution with various telescopes. We found that [N/Fe] scales with that of iron in the metallicity range -3.1 < [Fe/H] <0 with the slope 0.01+-0.02. Furthermore, we derive uniform and accurate (N/O) ratios using oxygen abundances from near-UV OH lines obtained in our previous studies. We find that a primary component of nitrogen is required to explain the observations. The NH lines are discovered in the VLT/UVES spectra of the very metal-poor subdwarfs G64-12 and LP815-43 indicating that these stars are N rich. The results are compared with theoretical models and observations of extragalactic HII regions and Damped Ly$\alpha$ systems. This is the first direct comparison of the (N/O) ratios in these objects with those in Galactic stars.Comment: 10 pages, 6 figures, to appear in Astronomy and Astrophysic