58 research outputs found
Effect of an optimised pelleted diet on Salmonella prevalence and pig productivity
The effect of an optimised, wheat based pelleted diet containing barley, sugar beet pulp and organic acids on Salmonella prevalence and pig productivity was investigated in two finisher herds. The optimised diet significantly reduced Salmonella seroprevalence compared to standard pelleted feed and meal feed. In contrast to previous studies, meal feed did not have a significant Salmonella reducing effect in this study. Meal diet but not the optimised diet had a significant negative effect on pig productivity, compared to the standard pelleted diet. Our results show that the optimised diet is a suitable alternative to wheat based pelleted feed or meal feed in reducing Salmonella prevalence in finisher pigs
Eclipsing binaries in open clusters. II. V453 Cyg in NGC 6871
We derive absolute dimensions of the early B-type detached eclipsing binary
V453 Cygni (B0.4 IV + B0.7 IV, P=3.89d), a member of the open cluster NGC 6871.
From the analysis of new, high-resolution, spectroscopy and the UBV light
curves of Cohen (1974) we find the masses to be 14.36 +/- 0.20 and 11.11 +/-
0.13 Msun, the radii to be 8.55 +/- 0.06 and 5.49 +/- 0.06 Rsun, and the
effective temperatures to be 26600 +/- 500 and 25 500 +/- 800 K for the primary
and secondary stars, respectively. The surface gravities of 3.731 +/- 0.012 and
4.005 +/- 0.015 indicate that V453 Cyg is reaching the end of its main sequence
lifetime. We have determined the apsidal motion period of the system to be 66.4
+/- 1.8 yr using the technique of Lacy (1992) extended to include spectroscopic
data as well as times of minimum light, giving a density concentration
coefficient of log(k_2) = -2.226 +/- 0.024. Contaminating (third) light has
been detected for the first time in the light curve of V453 Cyg; previous
analyses without this effect systematically underestimate the ratio of the
radii of the two stars. The absolute dimensions of the system have been
compared to the stellar evolution models of the Granada, Geneva, Padova and
Cambridge groups. All model sets fit the data on V453 Cyg for solar helium and
metal abundances and an age of 10.0 +/- 0.2 Myr. The Granada models also agree
fully with the observed log(k_2) once general relativistic effects have been
accounted for. The Cambridge models with convective core overshooting fit V453
Cyg better than those without. Given this success of the theoretical
predictions, we briefly discuss which eclipsing binaries should be studied in
order to further challenge the models.Comment: Accepted for publication in MNRAS (14 pages, 5 figures, Fig.4 reduced
in size
HAT Variability Survey in the High Stellar Density "Kepler Field" with Millimagnitude Image Subtraction Photometry
The Hungarian-made Automated Telescope network (HATnet) is an ongoing project
to detect transiting extra-solar planets using small aperture (11 cm diameter),
robotic telescopes. In this paper we present the results from using image
subtraction photometry to reduce a crowded stellar field observed with one of
the HATnet telescopes (HAT-5). This field was chosen to overlap with the
planned Kepler mission. We obtained I-band light curves for 98,000 objects in a
8.3x8.3 square degree field of view, near the Galactic plane in the
constellations Cygnus and Lyra. These observations include 788 5-minute
exposures over 30 days. For the brightest stars (I~8.0) we achieved a precision
of 3.5 millimagnitudes, falling to 0.1 magnitudes at the faint end (I~14). From
these light curves we identify 1617 variable stars, of which 1439 are newly
discovered. The fact that nearly 90% of the variables were previously
undetected further demonstrates the vast number of variables yet to be
discovered even among fairly bright stars in our Galaxy. We also discuss some
of the most interesting cases. These include: V1171 Cyg, a triple system with
the inner two stars in P=1.462 day period eclipsing orbit and the outer star a
P=4.86 day Cepheid; HD227269, an eccentric eclipsing system with a P=4.86 day
period that also shows P=2.907 day pulsations; WW Cyg, a well studied eclipsing
binary; V482 Cyg, an RCB star; and V546 Cyg, a PV Tel Variable. We also detect
a number of small amplitude variables, in some cases with full amplitude as low
as 10 mmag.Comment: 44 pages, 19 figures. Accepted for publication in the Astronomical
Journal. Revised version, including updated matches to existing catalogs.
Data available at http://cfa-www.harvard.edu/~gbakos/HAT/LC/199
Lattice Boltzmann simulations of soft matter systems
This article concerns numerical simulations of the dynamics of particles
immersed in a continuum solvent. As prototypical systems, we consider colloidal
dispersions of spherical particles and solutions of uncharged polymers. After a
brief explanation of the concept of hydrodynamic interactions, we give a
general overview over the various simulation methods that have been developed
to cope with the resulting computational problems. We then focus on the
approach we have developed, which couples a system of particles to a lattice
Boltzmann model representing the solvent degrees of freedom. The standard D3Q19
lattice Boltzmann model is derived and explained in depth, followed by a
detailed discussion of complementary methods for the coupling of solvent and
solute. Colloidal dispersions are best described in terms of extended particles
with appropriate boundary conditions at the surfaces, while particles with
internal degrees of freedom are easier to simulate as an arrangement of mass
points with frictional coupling to the solvent. In both cases, particular care
has been taken to simulate thermal fluctuations in a consistent way. The
usefulness of this methodology is illustrated by studies from our own research,
where the dynamics of colloidal and polymeric systems has been investigated in
both equilibrium and nonequilibrium situations.Comment: Review article, submitted to Advances in Polymer Science. 16 figures,
76 page
Accurate masses and radii of normal stars: modern results and applications
This paper presents and discusses a critical compilation of accurate,
fundamental determinations of stellar masses and radii. We have identified 95
detached binary systems containing 190 stars (94 eclipsing systems, and alpha
Centauri) that satisfy our criterion that the mass and radius of both stars be
known to 3% or better. To these we add interstellar reddening, effective
temperature, metal abundance, rotational velocity and apsidal motion
determinations when available, and we compute a number of other physical
parameters, notably luminosity and distance. We discuss the use of this
information for testing models of stellar evolution. The amount and quality of
the data also allow us to analyse the tidal evolution of the systems in
considerable depth, testing prescriptions of rotational synchronisation and
orbital circularisation in greater detail than possible before. The new data
also enable us to derive empirical calibrations of M and R for single (post-)
main-sequence stars above 0.6 M(Sun). Simple, polynomial functions of T(eff),
log g and [Fe/H] yield M and R with errors of 6% and 3%, respectively.
Excellent agreement is found with independent determinations for host stars of
transiting extrasolar planets, and good agreement with determinations of M and
R from stellar models as constrained by trigonometric parallaxes and
spectroscopic values of T(eff) and [Fe/H]. Finally, we list a set of 23
interferometric binaries with masses known to better than 3%, but without
fundamental radius determinations (except alpha Aur). We discuss the prospects
for improving these and other stellar parameters in the near future.Comment: 56 pages including figures and tables. To appear in The Astronomy and
Astrophysics Review. Ascii versions of the tables will appear in the online
version of the articl
AE Aquarii represents a new subclass of Cataclysmic Variables
We analyze properties of the unique nova-like star AE Aquarii identified with
a close binary system containing a red dwarf and a very fast rotating
magnetized white dwarf. It cannot be assigned to any of the three commonly
adopted sub-classes of Cataclysmic Variables: Polars, Intermediate Polars, and
Accreting non-magnetized White Dwarfs. Our study has shown that the white dwarf
in AE Aqr is in the ejector state and its dipole magnetic moment is . It switched into this state due to intensive mass
exchange between the system components during a previous epoch. A high rate of
disk accretion onto the white dwarf surface resulted in temporary screening of
its magnetic field and spin-up of the white dwarf to its present spin period.
Transition of the white dwarf to the ejector state had occurred at a final
stage of the spin-up epoch as its magnetic field emerged from the accreted
plasma due to diffusion. In the frame of this scenario AE Aqr represents a
missing link in the chain of Polars evolution and the white dwarf resembles a
recycled pulsar.Comment: accepted for publication in Astronomy Reports (July 2012
Comments on A.S.A. Z21.13.3 - 1956 Gravity and Fan Type Floor Furnaces
Peer reviewed: NoNRC publication: Ye
Comments on ASA Z21.11 - 1956 Gas Fired Room Heaters
Peer reviewed: NoNRC publication: Ye
Comments on ASA Z21.13.4 - 1955 Gravity and Fan Type Vented Recessed Heaters
Peer reviewed: NoNRC publication: Ye
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