Effects of spot structure of lines of rare earths and non-LTE effects on lithium abundance estimates for two roAp stars

Taking into account blending of the lithium 6108 Å line profile by adjacent rare-earth lines together with their spotted surface structure does not appreciably affect lithium abundance estimates for the atmospheres of HD 83368 and HD 60435 but provides a better fit of the observed and stimulated line profiles. Our computed non-LTE corrections reduce the lithium abundance estimates by 0.1-0.2 dex for both stars. Given the uncertainties in the lithium abundances, it is not possible to be certain whether the lithium abundances in map stars, or at least in their spots, exceed the cosmic (primordial) value. © 2002 MAIK "Nauka/Interperiodica"

Lithium and its isotopic ratio 6Li/7Li in the atmospheres of some sharp-lined roAp star

The lines of lithium at 6708 A, and 6103 A, are analyzed in high resolution spectra of some sharp-lined and slowly rotating roAp stars. Three spectral synthesis codes - STARSP, ZEEMAN2 and SYNTHM were used. New lines of the rare earth elements from the DREAM database, and lines calculated on the basis of the NIST energy levels were included. Magnetic splitting and other line broadening processes were taken into account. Enhanced abundances of lithium in the atmospheres of the stars studied are obtained for both the lithium lines. High estimates of 6Li/7Li ratio (0.2 -- 0.5) for the studied star can be explained by Galactic Cosmic Ray (GCR) production through the spallation reactions and the preservation of the original $^6$Li and $^7$Li by the strong magnetic fields.Comment: 5 pages, 2*5 figs, submitted for IAUS #224 Proceeding

A Search for Nitrogen-Enhanced Metal-Poor Stars

Theoretical models of very metal-poor intermediate-mass Asymptotic Giant Branch (AGB) stars predict a large overabundance of primary nitrogen. The very metal-poor, carbon-enhanced, s-process-rich stars, which are thought to be the polluted companions of now-extinct AGB stars, provide direct tests of the predictions of these models. Recent studies of the carbon and nitrogen abundances in metal-poor stars have focused on the most carbon-rich stars, leading to a potential selection bias against stars that have been polluted by AGB stars that produced large amounts of nitrogen, and hence have small [C/N] ratios. We call these stars Nitrogen-Enhanced Metal-Poor (NEMP) stars, and define them as having [N/Fe] > +0.5 and [C/N] < -0.5. In this paper, we report on the [C/N] abundances of a sample of 21 carbon-enhanced stars, all but three of which have [C/Fe] < +2.0. If NEMP stars were made as easily as Carbon-Enhanced Metal-Poor (CEMP) stars, then we expected to find between two and seven NEMP stars. Instead, we found no NEMP stars in our sample. Therefore, this observational bias is not an important contributor to the apparent dearth of N-rich stars. Our [C/N] values are in the same range as values reported previously in the literature (-0.5 to +2.0), and all stars are in disagreement with the predicted [C/N] ratios for both low-mass and high-mass AGB stars. We suggest that the decrease in [C/N] from the low-mass AGB models is due to enhanced extra-mixing, while the lack of NEMP stars may be caused by unfavorable mass ratios in binaries or the difficulty of mass transfer in binary systems with large mass ratios.Comment: 14 pages, 7 figures, to be published in Ap

Landscape, soil, lithology, climate and permafrost control on dissolved carbon, major and trace elements in the Ob River, Western Siberia

In order to foresee possible changes in the elementary composition of Arctic river waters, complex studies with extensive spatial coverage, including gradients in climate and landscape parameters, are needed. Here, we used the unique position of the Ob River, draining through the vast partially frozen peatlands of the western Siberia Lowland and encompassing a sizable gradient of climate, permafrost, vegetation, soils and Quaternary deposits, to assess a snap-shot (8–23 July 2016) concentration of all major and trace elements in the main stem (~3000 km transect from the Tom River confluence in the south to Salekhard in the north) and its 11 tributaries. During the studied period, corresponding to the end of the spring flood-summer baseflow, there was a systematic decrease, from the south to the north, of Dissolved Inorganic Carbon (DIC), Specific Conductivity, Ca and some labile trace elements (Mo, W and U). In contrast, Dissolved Organic Carbon (DOC), Fe, P, divalent metals (Mn, Ni, Cu, Co and Pb) and low mobile trace elements (Y, Nb, REEs, Ti, Zr, Hf and Th) sizably increased their concentration northward. The observed latitudinal pattern in element concentrations can be explained by progressive disconnection of groundwaters from the main river and its tributaries due to a northward increase in the permafrost coverage. A northward increase in bog versus forest coverage and an increase in DOC and Fe export enhanced the mobilization of insoluble, low mobile elements which were present in organo-ferric colloids (1 kDa—0.45 µm), as confirmed by an in-situ dialysis size fractionation procedure. The chemical composition of the sampled mainstream and tributaries demonstrated significant (p < 0.01) control of latitude of the sampling point; permafrost coverage; proportion of bogs, lakes and floodplain coverage and lacustrine and fluvio-glacial Quaternary deposits of the watershed. This impact was mostly pronounced on DOC, Fe, P, divalent metals (Mn, Co, Ni, Cu and Pb), Rb and low mobile lithogenic trace elements (Al, Ti, Cr, Y, Zr, Nb, REEs, Hf and Th). The pH and concentrations of soluble, highly mobile elements (DIC, SO4, Ca, Sr, Ba, Mo, Sb, W and U) positively correlated with the proportion of forest, loesses, eluvial, eolian, and fluvial Quaternary deposits on the watershed. Consistent with these correlations, a Principal Component Analysis demonstrated two main factors explaining the variability of major and trace element concentration in the Ob River main stem and tributaries. The DOC, Fe, divalent metals and trivalent and tetravalent trace elements were presumably controlled by a northward increase in permafrost, floodplain, bogs, lakes and lacustrine deposits on the watersheds. The DIC and labile alkaline-earth metals, oxyanions (Mo, Sb and W) and U were impacted by southward-dominating forest coverage, loesses and eluvial and fertile soils. Assuming that climate warming in the WSL will lead to a northward shift of the forest and permafrost boundaries, a “substituting space for time” approach predicts a future increase in the concentration of DIC and labile major and trace elements and a decrease of the transport of DOC and low soluble trace metals in the form of colloids in the main stem of the Ob River. Overall, seasonally-resolved transect studies of large riverine systems of western Siberia are needed to assess the hydrochemical response of this environmentally-important territory to on-going climate change

Клиническое наблюдение тонкокишечной непроходимости при множественных диоспиробезоарах желудочно-кишечного тракта

Abstract Small bowel obstruction (SBO) is 3-4% of all abdominal acute diseases. Small bowel obstruction due to bezoars is rare (2-4%), and is detected mainly in patients with predisposing risk factors: gastrointestinal motility disorders, psychiatric diseases, enzymatic insufficiency, previous bariatric surgery, diabetes mellitus and hypothyroidism complicated by gastroparesis. The leading role in the verification of small bowel obstruction in patients without surgical interventions on the abdominal organs should be given to computed tomography. According to the literature, the mortality from SBO due to bezoar may reach 30%. We present an unusual clinical case of recurrent small bowel obstruction with severe intestinal disease and septic shock induced by multiple phytobezoars and complicated with severe pseudomembranous colitis. Moreover, in our opinion, laparoscopic access can be used both for diagnostic and therapeutic purposes in patients with acute small bowel obstruction.РЕЗЮМЕ Острая кишечная непроходимость (ОКН) составляет 3-4% от всех неотложных заболеваний брюшной полости. Тонкокишечная непроходимость, обусловленная безоарами, встречается достаточно редко (2-4%) и выявляется, в основном, у пациентов с предрасполагающими факторами риска, такими как: нарушения моторики желудочно-кишечного тракта, психиатрические заболевания, ферментативная недостаточность, перенесенные бариартрические операции, сахарный диабет и гипотиреоз, осложненные гастропарезом. Ведущую роль в верификации тонкокишечной непроходимости у пациентов без оперативных вмешательств на органах брюшной полости в анамнезе следует отдавать компьютерной томографии. Летальность при ОКН, вызванной безоарами, может достигать, по данным литературы, 30%. Мы представляем необычный клинический случай рецидивирующей тонкокишечной непроходимости с тяжелой степенью кишечной недостаточности и исходом в септический шок, вызванной множественными фитобезоарами и отягощенной псевдомембранозным колитом тяжелой степени. При этом, по нашему мнению, лапароскопический доступ может быть использован как с диагностической, так и с лечебной целью у пациентов с острой тонкокишечной непроходимостью

Lithium and its isotopic ratio ⁶Li/⁷Li in the atmospheres of sharp-lined roAp stars γ Equulei and HD 166473

The lithium lines at 6708 Å for two sharp-lined roAp stars γ Equ and HD 166473 and at 6103 Å for γ Equ were analyzed in high resolution spectra. Three spectral synthesis codes – STARSP, ZEEMAN2, and SYNTHM – were used. New lines of the rare-earth elements from the DREAM database and lines calculated on the basis of the NIST energy levels were included. Magnetic splitting and other line broadening processes were taken into account. Enhanced abundances of lithium in the atmospheres of the stars and high estimates of ⁶Li/⁷Li ratio (0.2 ÷ 0.5) can be explained by the Galactic Cosmic Ray (GCR) production due to spallation reactions and the preservation of original ⁶Li and ⁷Li by strong magnetic fields