8,105 research outputs found
Comparison between persisting anti-lipopolysaccharide antibodies and culture at postmortem in salmonella-infected cattle herds
Complexity and non-separability of classical Liouvillian dynamics
We propose a simple complexity indicator of classical Liouvillian dynamics,
namely the separability entropy, which determines the logarithm of an effective
number of terms in a Schmidt decomposition of phase space density with respect
to an arbitrary fixed product basis. We show that linear growth of separability
entropy provides stricter criterion of complexity than Kolmogorov-Sinai
entropy, namely it requires that dynamics is exponentially unstable, non-linear
and non-markovian.Comment: Revised version, 5 pages (RevTeX), with 6 pdf-figure
Horizontal-branch morphology and multiple stellar populations in the anomalous globular cluster M22
M22 is an anomalous globular cluster that hosts two groups of stars with
different metallicity and s-element abundance. The star-to-star light-element
variations in both groups, with the presence of individual Na-O and C-N
anticorrelations, demonstrates that this Milky-Way satellite has experienced a
complex star-formation history. We have analysed FLAMES/UVES spectra for seven
stars covering a small color interval, on the reddest horizontal-branch (HB)
portion of this cluster and investigated possible relations between the
chemical composition of a star and its location along the HB. Our chemical
abundance analysis takes into account effects introduced by deviations from the
local-thermodynamic equilibrium (NLTE effects), that are significant for the
measured spectral lines in the atmospheric parameters range spanned by our
stars. We find that all the analysed stars are barium-poor and sodium-poor,
thus supporting the idea that the position of a star along the HB is strictly
related to the chemical composition, and that the HB-morphology is influenced
by the presence of different stellar populations.Comment: 21 pages, 3 figures, accepted for publication in Ap
Model of mobile agents for sexual interactions networks
We present a novel model to simulate real social networks of complex
interactions, based in a granular system of colliding particles (agents). The
network is build by keeping track of the collisions and evolves in time with
correlations which emerge due to the mobility of the agents. Therefore,
statistical features are a consequence only of local collisions among its
individual agents. Agent dynamics is realized by an event-driven algorithm of
collisions where energy is gained as opposed to granular systems which have
dissipation. The model reproduces empirical data from networks of sexual
interactions, not previously obtained with other approaches.Comment: 6 pages, 8 figure
Carbon and oxygen in metal-poor halo stars
Carbon and oxygen are key tracers of the Galactic chemical evolution; in
particular, a reported upturn in [C/O] towards decreasing [O/H] in metal-poor
halo stars could be a signature of nucleosynthesis by massive Population III
stars. We reanalyse carbon, oxygen, and iron abundances in thirty-nine
metal-poor turn-off stars. For the first time, we take into account
three-dimensional (3D) hydrodynamic effects together with departures from local
thermodynamic equilibrium (LTE) when determining both the stellar parameters
and the elemental abundances, by deriving effective temperatures from 3D
non-LTE H profiles, surface gravities from Gaia parallaxes, iron
abundances from 3D LTE Feii equivalent widths, and carbon and oxygen abundances
from 3D non-LTE Ci and Oi equivalent widths. We find that [C/Fe] stays flat
with [Fe/H], whereas [O/Fe] increases linearly up to dex with decreasing
[Fe/H] down to dex. As such [C/O] monotonically decreases towards
decreasing [O/H], in contrast to previous findings, mainly by virtue of less
severe non-LTE effects for Oi at low [Fe/H] with our improved calculations.Comment: 5 pages, 2 figures; published in A&A Letter
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