386 research outputs found
TB42: The Mycotoxic Effects of Fungi Isolated from Poultry Feed Ingredients: The Response of Ducklings and Performance of Commercial Broiler Chickens Fed Experimentally Infected Corn Diets
The present work, planned to investigate the possibility of mycotoxins occurring in feed ingredients fed to poultry in Maine, was designed with the following objectives: (1) to isolate fungi from poultry feed ingredients; (2) to grow the m separately on corn (the carbohydrate source of poultry rations) for later mixing into the diets; (3) to test the variously infected lots of this corn substrate for mycotoxicity by feeding ducklings, a bioindicator for toxins; (4) to determine the effects of aflatoxin and other mycotoxins from feed ingredients, on the performance of commercial broiler chickens; and (5) to appraise this response as a measure of toxicity of the fungi found in feed ingredients.https://digitalcommons.library.umaine.edu/aes_techbulletin/1159/thumbnail.jp
5-dimensional contact SO(3)-manifolds and Dehn twists
In this paper the 5-dimensional contact SO(3)-manifolds are classified up to
equivariant contactomorphisms. The construction of such manifolds with singular
orbits requires the use of generalized Dehn twists.
We show as an application that all simply connected 5-manifoldswith singular
orbits are realized by a Brieskorn manifold with exponents (k,2,2,2). The
standard contact structure on such a manifold gives right-handed Dehn twists,
and a second contact structure defined in the article gives left-handed twists.Comment: 16 pages, 1 figure; simplification of arguments by restricting
classification to coorientation preserving contactomorphism
Stellar science from a blue wavelength range - A possible design for the blue arm of 4MOST
From stellar spectra, a variety of physical properties of stars can be
derived. In particular, the chemical composition of stellar atmospheres can be
inferred from absorption line analyses. These provide key information on large
scales, such as the formation of our Galaxy, down to the small-scale
nucleosynthesis processes that take place in stars and supernovae. By extending
the observed wavelength range toward bluer wavelengths, we optimize such
studies to also include critical absorption lines in metal-poor stars, and
allow for studies of heavy elements (Z>38) whose formation processes remain
poorly constrained. In this context, spectrographs optimized for observing blue
wavelength ranges are essential, since many absorption lines at redder
wavelengths are too weak to be detected in metal-poor stars. This means that
some elements cannot be studied in the visual-redder regions, and important
scientific tracers and science cases are lost. The present era of large public
surveys will target millions of stars. Here we describe the requirements
driving the design of the forthcoming survey instrument 4MOST, a multi-object
spectrograph commissioned for the ESO VISTA 4m-telescope. We focus here on
high-density, wide-area survey of stars and the science that can be achieved
with high-resolution stellar spectroscopy. Scientific and technical
requirements that governed the design are described along with a thorough line
blending analysis. For the high-resolution spectrograph, we find that a
sampling of >2.5 (pixels per resolving element), spectral resolution of 18000
or higher, and a wavelength range covering 393-436 nm, is the most
well-balanced solution for the instrument. A spectrograph with these
characteristics will enable accurate abundance analysis (+/-0.1 dex) in the
blue and allow us to confront the outlined scientific questions. (abridged)Comment: 14 pages, 8 figures, accepted for publication in A
Inequivalent contact structures on Boothby-Wang 5-manifolds
We consider contact structures on simply-connected 5-manifolds which arise as
circle bundles over simply-connected symplectic 4-manifolds and show that
invariants from contact homology are related to the divisibility of the
canonical class of the symplectic structure. As an application we find new
examples of inequivalent contact structures in the same equivalence class of
almost contact structures with non-zero first Chern class.Comment: 27 pages; to appear in Math. Zeitschrif
GEMS: Galaxy Evolution from Morphologies and SEDs
GEMS, Galaxy Evolution from Morphologies and SEDs, is a large-area (800
arcmin2) two-color (F606W and F850LP) imaging survey with the Advanced Camera
for Surveys on HST. Centered on the Chandra Deep Field South, it covers an area
of ~28'x28', or about 120 Hubble Deep Field areas, to a depth of
m_AB(F606W)=28.3 (5sigma and m_AB(F850LP)=27.1 (5sigma) for compact sources. In
its central ~1/4, GEMS incorporates ACS imaging from the GOODS project.
Focusing on the redshift range 0.2<=z<=1.1, GEMS provides morphologies and
structural parameters for nearly 10,000 galaxies where redshift estimates,
luminosities and SEDs exist from COMBO-17. At the same time, GEMS contains
detectable host galaxy images for several hundred faint AGN. This paper
provides an overview of the science goals, the experiment design, the data
reduction and the science analysis plan for GEMS.Comment: 24 pages, TeX with 6 eps Figures; to appear in ApJ Supplement. Low
resolution figures only. Full resolution at
http://zwicky.as.arizona.edu/~rix/Misc/GEMS.ps.g
The stellar host in blue compact dwarf galaxies: the need for a two-dimensional fit
The structural properties of the low surface brightness stellar host in blue
compact dwarf galaxies are often studied by fitting r^{1/n} models to the outer
regions of their radial profiles. The limitations imposed by the presence of a
large starburst emission overlapping the underlying component makes this kind
of analysis a difficult task. We propose a two-dimensional fitting methodology
in order to improve the extraction of the structural parameters of the LSB
host. We discuss its advantages and weaknesses by using a set of simulated
galaxies and compare the results for a sample of eight objects with those
already obtained using a one-dimensional technique. We fit a PSF convolved
Sersic model to synthetic galaxies, and to real galaxy images in the B, V, R
filters. We restrict the fit to the stellar host by masking out the starburst
region and take special care to minimize the sky-subtraction uncertainties. In
order to test the robustness and flexibility of the method, we carry out a set
of fits with synthetic galaxies. Furthermore consistency checks are performed
to assess the reliability and accuracy of the derived structural parameters.
The more accurate isolation of the starburst emission is the most important
advantage and strength of the method. Thus, we fit the host galaxy in a range
of surface brightness and in a portion of area larger than in previous
published 1D fits with the same dataset. We obtain robust fits for all the
sample galaxies, all of which, except one, show Sersic indices n very close to
1, with good agreement in the three bands. These findings suggest that the
stellar hosts in BCDs have near-exponential profiles, a result that will help
us to understand the mechanisms that form and shape BCD galaxies, and how they
relate to the other dwarf galaxy classes.Comment: 22 pages, 15 figures (low resolution), accepted for publication in
A&A. A higher resolution version of the figures can be provided upon reques
Geometrical tests of cosmological models. III. The cosmology-evolution diagram at z=1
The rotational velocity of distant galaxies, when interpreted as a size
(luminosity) indicator, may be used as a tool to select high redshift standard
rods (candles) and probe world models and galaxy evolution via the classical
angular diameter-redshift or Hubble diagram tests. We implement the proposed
testing strategy using a sample of 30 rotators spanning the redshift range
0.2<z<1 with high resolution spectra and images obtained by the VIMOS/VLT Deep
Redshift Survey (VVDS) and the Great Observatories Origins Deep Survey (GOODs).
We show that by applying at the same time the angular diameter-redshift and
Hubble diagrams to the same sample of objects (i.e. velocity selected galactic
discs) one can derive a characteristic chart, the cosmology-evolution diagram,
mapping the relation between global cosmological parameters and local
structural parameters of discs such as size and luminosity. This chart allows
to put constraints on cosmological parameters when general prior information
about discs evolution is available. In particular, by assuming that equally
rotating large discs cannot be less luminous at z=1 than at present (M(z=1) <
M(0)), we find that a flat matter dominated cosmology (Omega_m=1) is excluded
at a confidence level of 2sigma and an open cosmology with low mass density
(Omega_m = 0.3) and no dark energy contribution is excluded at a confidence
level greater than 1 sigma. Inversely, by assuming prior knowledge about the
cosmological model, the cosmology-evolution diagram can be used to gain useful
insights about the redshift evolution of the structural parameters of baryonic
discs hosted in dark matter halos of nearly equal masses.Comment: 14 pages and 11 figures. A&A in pres
SS Ari: a shallow-contact close binary system
Two CCD epochs of light minimum and a complete R light curve of SS Ari are
presented. The light curve obtained in 2007 was analyzed with the 2003 version
of the W-D code. It is shown that SS Ari is a shallow contact binary system
with a mass ratio and a degree of contact factor f=9.4(\pm0.8%). A
period investigation based on all available data shows that there may exist two
distinct solutions about the assumed third body. One, assuming eccentric orbit
of the third body and constant orbital period of the eclipsing pair results in
a massive third body with and P_3=87.00.278M_{\odot}$. Both of the cases
suggest the presence of an unseen third component in the system.Comment: 28 pages, 9 figures and 5 table
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