4,802 research outputs found
O/Fe in metal-poor main sequence and subgiant stars
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
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
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
Method of raising meat producing animals to increase lean tissue development
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
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
Non-LTE analysis of copper abundances for the two distinct halo populations in the solar neighborhood
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
Feed compositions for domestics animals containing hydroxymethylbutyrate
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
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
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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