4,780 research outputs found

    O/Fe in metal-poor main sequence and subgiant stars

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    A study of the O/Fe ratio in metal-poor main sequence and subgiant stars is presented using the [OI] 6300A line, the OI 7774A triplet, and a selection of weak FeII lines observed on high-resolution spectra acquired with the VLT UVES spectrograph. The [OI] line is detected in the spectra of 18 stars with -0.5 < [Fe/H] < -2.4, and the triplet is observed for 15 stars with [Fe/H] ranging from -1.0 to -2.7. The abundance analysis was made first using standard model atmospheres taking into account non-LTE effects on the triplet: the [OI] line and the triplet give consistent results with [O/Fe] increasing quasi-linearly with decreasing [Fe/H] reaching [O/Fe] ~ +0.7 at [Fe/H] = -2.5. When hydrodynamical model atmospheres representing stellar granulation in dwarf and subgiant stars replace standard models, the [O/Fe] from the [OI] and FeII lines is decreased by an amount which increases with decreasing [Fe/H]. The [O/Fe] vs [Fe/H] relation remains quasi-linear extending to [O/Fe] ~ +0.5 at [Fe/H] = -2.5, but with a tendency of a plateau with [O/Fe] ~ +0.3 for -2.0 < [Fe/H] < -1.0, and a hint of cosmic scatter in [O/Fe] at [Fe/H] ~ -1.0. Use of the hydrodynamical models disturbs the broad agreement between the oxygen abundances from the [OI], OI, and OH lines, but 3D non-LTE effects may serve to erase these differences.Comment: ps file, 18 pages (including 10 figures) - Accepted for publication in A&

    Memory and remembrance in selected nonfiction works of Elie Wiesel

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    Although nonfictional writing provides critical insights into history in ways that fictional writing never could, it is very often relegated to a “second-class citizen” status in the realm of literary criticism and appreciation. Literacy tradition has created a hard line between literature, specifically novels and short stories and poetry, which we regard as created fictions and nonliterary test – journalism, biography, history, essays, and so on- which we think of as records of actuality. This distinction is what prevents us from applying to nonfiction the analytical tools we use to uncover the secrets of literary art. (McCord 748

    Method of feeding ketoisocaproate to lactating domestic mammals

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    Lactating domestic mammals are fed ketoisocaproate (KIC) with a diet containing limited leucine to improve the quantity and quality of the milk produced. This feeding method is particularly applicable to dairy cattle but also can advantageously be used with nursing domestic animals including cattle, sheep, goats, horses, and swine

    Non-LTE analysis of copper abundances for the two distinct halo populations in the solar neighborhood

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    Two distinct halo populations were found in the solar neighborhood by a series of works. They can be clearly separated by [alpha\Fe] and several other elemental abundance ratios including [Cu/Fe]. Very recently, a non-local thermodynamic equilibrium (non-LTE) study revealed that relatively large departures exist between LTE and non-LTE results in copper abundance analysis. We aim to derive the copper abundances for the stars from the sample of Nissen et al (2010) with both LTE and non-LTE calculations. Based on our results, we study the non-LTE effects of copper and investigate whether the high-alpha population can still be distinguished from the low-alpha population in the non-LTE [Cu/Fe] results. Our differential abundance ratios are derived from the high-resolution spectra collected from VLT/UVES and NOT/FIES spectrographs. Applying the MAFAGS opacity sampling atmospheric models and spectrum synthesis method, we derive the non-LTE copper abundances based on the new atomic model with current atomic data obtained from both laboratory and theoretical calculations. The copper abundances determined from non-LTE calculations are increased by 0.01 to 0.2 dex depending on the stellar parameters compared with the LTE results. The non-LTE [Cu/Fe] trend is much flatter than the LTE one in the metallicity range -1.6<[Fe/H]<-0.8. Taking non-LTE effects into consideration, the high- and low-alpha stars still show distinguishable copper abundances, which appear even more clear in a diagram of non-LTE [Cu/Fe] versus [Fe/H]. The non-LTE effects are strong for copper, especially in metal-poor stars. Our results confirmed that there are two distinct halo populations in the solar neighborhood. The dichotomy in copper abundance is a peculiar feature of each population, suggesting that they formed in different environments and evolved obeying diverse scenarios.Comment: 9 pages, 7 figures, 2 table

    Method of raising meat producing animals to increase lean tissue development

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    A method is provided for raising meat producing domestic animals to increase lean tissue development. β-hydroxcy-β-methylbutyric acid or an edible salt thereof (HMB) is administered to the animals in an effective amount for a sufficient length of time to obtain a substantial increase in lean tissue weight. Feed compositions for use in practicing the method are also provided. The method and feed compositions are particularly adapted for use with ruminants, including beef cattle and lambs, since HMB is not subject to appreciable rumen destruction. The method can also be practiced with other domestic animals, including chickens, and turkeys

    Method of enhancing immune response of mammals

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    β-methyl-βbutyrate (HMB) has been found to be markedly more effective for activating the immune function of T lymphocytes of mammals than α-ketoisocaproate (KIC). For activation of the T lymphocytes, β-methyl-butyric acid or an edible water-soluble salt thereof is administered to the mammal by a route through which the HMB enters the blood of the mammal. The amount administered is sufficient for effective enhancement of the blastogenesis of their T lymphocytes. The method is adapted for use with domestic mammals, including particularly cattle, sheep, and swine. HMB can also be used with humans as an immune system stimulant.</p

    Feed compositions for domestics animals containing hydroxymethylbutyrate

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    Feed compositions are provided for raising meat-producing ruminants and polutry. β-hydroxcy-β-methylbutyric acid or an edible salt thereof (HMB) is incorporated in the ruminant or poultry feeds to obtain a substantial increase in meat and/or to improve the quality of the lean meat

    Method of feeding ketoisocaproate to cattle and sheep

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    Cattle and sheep are fed ketoisocaproate (KIC) with a diet of limited leucine content for enhancement of growth and feed efficiency. The method is especially applicable to beef cattle and sheep being raised for meat production, but it can also be used with veal calves and mature sheep being fed for wool production

    The First Galaxies: Clues from Element Abundances

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    It has recently become possible to measure directly the abundances of several chemical elements in a variety of environments at redshifts up to z = 5. In this review I summarise the latest observations of Lyman break galaxies, damped Lyman alpha systems and the Lyman alpha forest with a view to uncovering any clues which these data may offer to the first episodes of star formation. The picture which is emerging is one where the universe at z = 3 already included many of the components of today's galaxies--even at these early times we see evidence for Populations I and II stars, while the `smoking gun' for Population III objects may be hidden in the chemical composition of the lowest density regions of the IGM, yet to be deciphered.Comment: 15 pages, LaTex, 8 Postscript Figures. To appear in the Philosophical Transactions of The Royal Society, Series
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