1,809 research outputs found
WASP-1: A lithium- and metal-rich star with an oversized planet
In this paper we present our results of a comprehensive spectroscopicanalysis
of WASP-1, the host star to the exoplanet WASP-1b. We derive T_eff = 6110 +/-
45 K, log g = 4.28 +/- 0.15, and [M/H] = 0.23 +/- 0.08, and also a high
abundance of lithium, log n(Li) = 2.91 +/- 0.05. These parameters suggests an
age for the system of 1-3 Gyr and a stellar mass of 1.25-1.35 M_sun. This means
that WASP-1 has properties very similar to those of HD 149026, the host star
for the highest density planet yet detected. Moreover, their planets orbit at
comparable distances and receive comparable irradiating fluxes from their host
stars. However, despite the similarity of WASP-1 with HD 149026, their planets
have strongly different densities. This suggests that gas-giant planet density
is not a simple function of host-star metallicity or of radiation environment
at ages of ~2 Gyr.Comment: Accepted for publication in MNRAS. 6 pages, 4 figure
Accountable Care Organizations are too small and loosely affiliated for financial bonuses to be effective at improving performance.
One part of the Affordable Care Act – or Obamacare – has an attempt to tackle the fragmentation of US health care delivery through the introduction of Accountable Care Organizations (ACOs). These organizations contract to provide care to large groups of Medicare recipients and there are group incentives for care to be provided more cost effectively. In new research Brigham Frandsen and James B. Rebitzer find that ACO’s relatively large sizes and loose setups mean that more powerful incentives are needed to reach cost-reduction targets. They write that for an ACO to achieve a cost reduction of 6 percent, bonuses would need to exceed 12 percent of costs – twice the intended savings
Efficient Algorithms for gcd and Cubic Residuosity in the Ring of Eisenstein Integers
We present simple and efficient algorithms for computing gcd and cubic residuosity in the ring of Eisenstein integers, Z[zeta] , i.e. the integers extended with zeta , a complex primitive third root of unity. The algorithms are similar and may be seen as generalisations of the binary integer gcd and derived Jacobi symbol algorithms. Our algorithms take time O(n^2) for n bit input. This is an improvement from the known results based on the Euclidian algorithm, and taking time O(n· M(n)), where M(n) denotes the complexity of multiplying n bit integers. The new algorithms have applications in practical primality tests and the implementation of cryptographic protocols. The technique underlying our algorithms can be used to obtain equally fast algorithms for gcd and quartic residuosity in the ring of Gaussian integers, Z[i]
Halo independent comparison of direct dark matter detection data
We extend the halo-independent method of Fox, Liu, and Weiner to include
energy resolution and efficiency with arbitrary energy dependence, making it
more suitable for experiments to use in presenting their results. Then we
compare measurements and upper limits on the direct detection of low mass
( GeV) weakly interacting massive particles with spin-independent
interactions, including the upper limit on the annual modulation amplitude from
the CDMS collaboration. We find that isospin-symmetric couplings are severely
constrained both by XENON100 and CDMS bounds, and that isospin-violating
couplings are still possible at the lowest energies, while the tension of the
higher energy CoGeNT bins with the CDMS modulation constraint remains. We find
the CRESST II signal is not compatible with the modulation signals of DAMA and
CoGeNT.Comment: version slightly longer than the first, with 3 additional figures and
the latest XENON100 bound added. 7 pages, 5 figure
Variable stars in the Open Cluster M11 (NGC 6705)
V-band time-series CCD photometric observations of the intermediate-age open
cluster M11 were performed to search for variable stars. Using these
time-series data, we carefully examined light variations of all stars in the
observing field. A total of 82 variable stars were discovered, of which 39
stars had been detected recently by Hargis et al. (2005). On the basis of
observational properties such as variable period, light curve shape, and
position on a color-magnitude diagram, we classified their variable types as 11
delta Scuti-type pulsating stars, 2 gamma Doradus-type pulsating stars, 40 W
UMa-type contact eclipsing binaries, 13 Algol-type detached eclipsing binaries,
and 16 eclipsing binaries with long period. Cluster membership for each
variable star was deduced from the previous proper motion results (McNamara et
al. 1977) and position on the color-magnitude diagram. Many pulsating stars and
eclipsing binaries in the region of M11 are probable members of the cluster.Comment: 23 pages, 9 figures, 3 tables, and accepted for publication in PAS
Anomalous Particle Size Dependence of Magnetic Relaxation Phenomena in Goethite Nanoparticles
By use of Mössbauer spectroscopy we have studied the magnetic properties of samples of goethite nanoparticles with different particle size. The spectra are influenced by fluctuations of the magnetization directions, but the size dependence is not in accordance with the Néel-Brown expression for superparamagnetic relaxation of the magnetization vectors of the particles as a whole. The data suggest that the magnetic fluctuations can be explained by fluctuations of the magnetization directions of small interacting grains within the particles
Efficient four fragment cloning for the construction of vectors for targeted gene replacement in filamentous fungi
<p>Abstract</p> <p>Background</p> <p>The rapid increase in whole genome fungal sequence information allows large scale functional analyses of target genes. Efficient transformation methods to obtain site-directed gene replacement, targeted over-expression by promoter replacement, in-frame epitope tagging or fusion of coding sequences with fluorescent markers such as GFP are essential for this process. Construction of vectors for these experiments depends on the directional cloning of two homologous recombination sequences on each side of a selection marker gene.</p> <p>Results</p> <p>Here, we present a USER Friendly cloning based technique that allows single step cloning of the two required homologous recombination sequences into different sites of a recipient vector. The advantages are: A simple experimental design, free choice of target sequence, few procedures and user convenience. The vectors are intented for <it>Agrobacterium tumefaciens </it>and protoplast based transformation technologies. The system has been tested by the construction of vectors for targeted replacement of 17 genes and overexpression of 12 genes in <it>Fusarium graminearum</it>. The results show that four fragment vectors can be constructed in a single cloning step with an average efficiency of 84% for gene replacement and 80% for targeted overexpression.</p> <p>Conclusion</p> <p>The new vectors designed for USER Friendly cloning provided a fast reliable method to construct vectors for targeted gene manipulations in fungi.</p
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