3,969 research outputs found
The Most Metal-Poor Stars. V. The CEMP-no Stars in 3D and Non-LTE
We explore the nature of carbon-rich ([C/Fe]_{1D,LTE} > +0.7), metal-poor
([Fe/H_{1D,LTE}] < -2.0) stars in the light of post 1D,LTE literature analyses,
which provide 3D-1D and NLTE-LTE corrections for iron, and 3D-1D corrections
for carbon (from the CH G-band, the only indicator at lowest [Fe/H]).
High-excitation C~I lines are used to constrain 3D,NLTE corrections of G-band
analyses. Corrections to the 1D,LTE compilations of Yoon et al. and Yong et al.
yield 3D,LTE and 3D,NLTE Fe and C abundances. The number of CEMP-no stars in
the Yoon et al. compilation (plus eight others) decreases from 130 (1D,LTE) to
68 (3D,LTE) and 35 (3D,NLTE). For stars with -4.5 < [Fe/H] < -3.0 in the
compilation of Yong et al., the corresponding CEMP-no fractions change from
0.30 to 0.15 and 0.12, respectively.
We present a toy model of the coalescence of pre-stellar clouds of the two
populations that followed chemical enrichment by the first zero-heavy-element
stars: the C-rich, hyper-metal-poor and the C-normal, very-metal-poor
populations. The model provides a reasonable first-order explanation of the
distribution of the 1D,LTE abundances of CEMP-no stars in the A(C) and [C/Fe]
vs. [Fe/H] planes, in the range -4.0 < [Fe/H] < -2.0.
The Yoon et al. CEMP Group I contains a subset of 19 CEMP-no stars (14% of
the group), 4/9 of which are binary, and which have large [Sr/Ba]_{1D,LTE}
values. The data support the conjectures of Hansen et al. (2016b, 2019) and
Arentsen et al. (2018) that these stars may have experienced enrichment from
AGB stars and/or "spinstars".Comment: ApJ in pres
Heavy metals and nitrogen in mosses: spatial patterns in 2010/2011 and long-term temporal trends in Europe
Naturally-occurring mosses have been sampled across Europe to monitor
the deposition of heavy metals and nitrogen from the air. This survey has been
repeated at five-yearly intervals since 1990 for heavy metals and since 2005 for
nitrogen. In 2010/2011, mosses were collected at ca. 4,500 sites in 25 countries
for heavy metals and ca. 2,400 sites in 15 countries for nitrogen. In general, the
lowest concentrations in mosses were found in northern Europe for both heavy
metals and nitrogen. The highest concentrations of heavy metals were often
observed in south-eastern Europe, whereas the highest concentrations of
nitrogen were found in parts of western and central Europe. Europe-wide the
concentration of lead (77% decline), vanadium (57%), iron (52%) and cadmium
(51%) has declined the most since 1990, whereas the concentration of copper
has declined the least (11% decline). Since 1995, the concentration of arsenic and
mercury has declined by 26% and 23% respectively. The nitrogen concentration
in mosses has hardly changed since 2005
Transformation techniques for the parameter estimation of discrete-time transfer functions
Imperial Users onl
Writing about war: making sense of the absurd in Mileta Prodanović's novel Pleši, čudovište, na moju nežnu muziku (Dance, you monster, to my soft music)
In the narrative of a mass conflict, the human experience of its effects may be subsumed into the rationalizing contours of history, or they may fall completely outside our comprehension. This article examines the intertextual strategies employed in Prodanović's novel about the war in former Yugoslavia. The text conveys the reality of the conflict by relating it through events and characters located in prior media constructions. The historical, documentary, mythic, and fictional sources focus on the signifying systems which drag the war into the horizon of expectations of those who were not there, closing the gap between reality and representation, life and art
How Close Are We to Solving the Puzzle? Review of the Alopecia Areata Research Workshop David Norris
- …