5,913 research outputs found
The lithium isotope ratio in the metal-poor halo star G271-162 from VLT/UVES observations
A high resolution (R = 110.000), very high S/N (>600) spectrum of the
metal-poor turnoff star G271-162 has been obtained in connection with the
commissioning of UVES at VLT/Kueyen. Using both 1D hydrostatic and 3D
hydrodynamical model atmospheres, the lithium isotope ratio has been estimated
from the LiI 670.8 nm line by means of spectral synthesis. The necessary
stellar line broadening (1D: macroturbulence + rotation, 3D: rotation) has been
determined from unblended KI, CaI and FeI lines. The 3D line profiles agree
very well with the observed profiles, including the characteristic line
asymmetries. Both the 1D and 3D analyses reveal a possible detection of 6Li in
G271-162, 6Li/7Li = 0.02 +-0.01 (one sigma). It is discussed if the smaller
amount of 6Li in G271-162 than in the similar halo star HD84937 could be due to
differences in stellar mass and/or metallicity or whether it may reflect an
intrinsic scatter of the Li isotope ratio in the ISM at a given metallicity.Comment: 5 pages with 6 figures. Accepted as a letter in A&
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
Para uma reorganização do serviço pĂșblico de media: responsabilidade social, independĂȘncia institucional e autonomia editorial no quadro da relação problemĂĄtica entre o Estado e o mercado
O debate em torno dos media de serviço pĂșblico aborda com frequĂȘncia, e por boas razĂ”es, o quĂŁo justificĂĄvel Ă© o envolvimento pĂșblico no mercado dos meios de comunicação social e â para aqueles que o aceitem â a natureza do seu papel, do seu campo de operaçÔes e dos conteĂșdos e serviços disponibilizados. Estas questĂ”es definem o campo de batalha central, onde se joga o destino e o papel dos media de serviço pĂșblico. Aos assuntos de governança Ă© dispensada menor atenção. Se aceitarmos que os media pĂșblicos desempenham um papel importante nas esferas cultural e polĂtica das sociedades europeias, como deverĂĄ o fornecimento dos seus serviços ser organizado? Como se conseguirĂĄ encontrar o delicado equilĂbrio entre controlo pĂșblico, responsabilização e autonomia editorial? Estas questĂ”es, que constituirĂŁo o objecto deste capĂtulo, sĂŁo muitas vezes consideradas um subtema burocrĂĄtico por pessoas com interesses especĂficos e conhecimentos especializados, como Ă© o caso de funcionĂĄrios pĂșblicos nas autoridades de regulação, advogados em grupos privados de comunicação, acadĂ©micos, ou gestores/administradores de media pĂșblicos. No entanto, a temĂĄtica deve atrair agora maior atenção, uma vez que as questĂ”es de governação podem constituir o novo â e mais subtil â campo de batalha, no qual os grupos privados de comunicação procuram novas oportunidades, apĂłs verificarem que o seu ataque Ă prĂłpria existĂȘncia dos seus congĂ©neres pĂșblicos nĂŁo se traduziu numa vitĂłria clara
Mapping Digital Media Series: Questionable Gains from the Digital Dividend
Having examined reports from numerous countries at various stages of completing the switch from analogue to digital terrestrial broadcasting produced by the Open Society Foundationâs Mapping Digital Media Project, Christian S. Nissen of the Copenhagen Business School and former CEO of the Danish Broadcasting Corporation argues that civil society in most countries is not seeing the benefits that could potentially be gained in terms of media pluralism
Development and Daily Management of an Explicit Strategy of Nonuse of Antimicrobial Drugs in Twelve Danish Organic Dairy Herds
Promotion of animal health and well-being at the individual animal and herd level is an important goal in organic farming. At the same time, chemical products affecting the natural balance among living organisms are prohibited in all areas of the organic farm. From an animal welfare point of view, however, no animal must suffer. Therefore, veterinary drugs are allowed under the European Unionâs regulations for organic farming, despite the fact that they are powerful cell toxins affecting both pathogenic and necessary bacteria, and as such in organic terminology, are regarded as âchemicalâ or âartificialâ products. In this article, we present and discuss interviews with 12 Danish organic dairy producers who claim that minimized use or nonuse of antimicrobial drugs is an explicit goal. The dairy producers were at different levels with regard to reduced antimicrobial treatment. An explicit strategy of no antimicrobial treatments is based primarily on a long-term effort to improve herd health, and secondarily, on finding alternative treatments for diseased animals. Improved hygiene, outdoor access, use of nursing cows, and blinding of chronic mastitis quarters were the main techniques in developing a strategy of not using antimicrobial treatments in the herd by dairy
producers. Producersâ perception of disease changed from something unavoidable to a disturbing break in the daily rhythm that often could have been avoided. Change toward a nonantimicrobial strategy was gradual and stepwise. All dairy producers in this study desired to preserve the possibility of using antimicrobial drugs in emergencies
Danish Stable Schools for Experiential Common Learning in Groups of Organic Dairy Farmers
The farmer field school (FFS) is a concept for farmersâ learning, knowledge exchange, and empowerment that has been developed and used in developing countries. In Denmark, a research project focusing on explicit nonantibiotic strategies involves farmers who have actively expressed an interest in phasing out antibiotics from their herds through promotion of animal health. One way of reaching this goal was to form participatory focused farmer groups in an FFS approach, which was adapted to Danish conditions and named âstable schools.â Four stable schools were established and went through a 1-yr cycle with 2 visits at each of the 5 or 6 farms connected to each group. A facilitator was connected to each group whose role was to write the meeting agenda together with the host farmer, direct the meeting, and write the minutes to send to the group members ater the meeting. Through group focus interviews and individual semistructured qualitative interviews of all participants, the approach of the farmersâ goal-directed work toward a common goal was judged to be very valuable and fruitful and based on a common learning process. Complex farming situations were the focus of all groups and in this context, problems were identified and solutions proposed based on each farmerâs individual goals. In this article, we describe the experiences of 4 stable school groups (each comprising farmers and a facilitator), and the common process of building a concept that is suitable for Danish organic dairy farming
Absolute Magnitude Calibration for Giants based on the Colour-Magnitude Diagrams of Galactic Clusters. II-Calibration with SDSS
We present an absolute magnitude calibration for red giants with the colour
magnitude diagrams of six Galactic clusters with different metallicities i.e.
M92, M13, M3, M71, NGC 6791 and NGC 2158. The combination of the absolute
magnitudes of the red giant sequences with the corresponding metallicities
provides calibration for absolute magnitude estimation for red giants for a
given colour. The calibration is defined in the colour interval
0.45 1.30 mag and it covers the metallicity interval
+0.37 dex. The absolute magnitude
residuals obtained by the application of the procedure to another set of
Galactic clusters lie in the interval mag.
However, the range of 94% of the residuals is shorter,
mag. The mean and the standard deviation of (all) residuals are 0.169 and 0.140
mag, respectively. The derived relations are applicable to stars older than 2
Gyr, the age of the youngest calibrating cluster.Comment: 12 pages, including 5 figures and 10 tables, accepted for publication
in PASA. arXiv admin note: substantial text overlap with arXiv:1204.429
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
A New Limit on Signals of Lorentz Violation in Electrodynamics
We describe the results of an experiment to test for spacetime anisotropy
terms that might exist from Lorentz violations. The apparatus consists of a
pair of cylindrical superconducting cavity-stabilized oscillators operating in
the TM_{010} mode with one axis east-west and the other vertical. Spatial
anisotropy is detected by monitoring the beat frequency at the sidereal rate
and its first harmonic. We see no anisotropy to a part in 10^{13}. This puts a
comparable bound on four linear combinations of parameters in the general
Standard Model extension, and a weaker bound of <4 x 10^{-9} on three others.Comment: 4 pages, 3 figures, 2 table
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