13,558 research outputs found
Determining the Mass of Kepler-78b With Nonparametric Gaussian Process Estimation
Kepler-78b is a transiting planet that is 1.2 times the radius of Earth and
orbits a young, active K dwarf every 8 hours. The mass of Kepler-78b has been
independently reported by two teams based on radial velocity measurements using
the HIRES and HARPS-N spectrographs. Due to the active nature of the host star,
a stellar activity model is required to distinguish and isolate the planetary
signal in radial velocity data. Whereas previous studies tested parametric
stellar activity models, we modeled this system using nonparametric Gaussian
process (GP) regression. We produced a GP regression of relevant Kepler
photometry. We then use the posterior parameter distribution for our
photometric fit as a prior for our simultaneous GP + Keplerian orbit models of
the radial velocity datasets. We tested three simple kernel functions for our
GP regressions. Based on a Bayesian likelihood analysis, we selected a
quasi-periodic kernel model with GP hyperparameters coupled between the two RV
datasets, giving a Doppler amplitude of 1.86 0.25 m s and
supporting our belief that the correlated noise we are modeling is
astrophysical. The corresponding mass of 1.87 M
is consistent with that measured in previous studies, and more robust due to
our nonparametric signal estimation. Based on our mass and the radius
measurement from transit photometry, Kepler-78b has a bulk density of
6.0 g cm. We estimate that Kepler-78b is 3226% iron
using a two-component rock-iron model. This is consistent with an Earth-like
composition, with uncertainty spanning Moon-like to Mercury-like compositions.Comment: 10 pages, 5 figures, accepted to ApJ 6/16/201
Quasinormal Modes and Stability Criterion of Dilatonic Black Hole in 1+1 and 4+1 Dimensions
We study the stability of black holes that are solutions of the dilaton
gravity derived from string-theoretical models in two and five dimensions
against to scalar field perturbations, using the Quasinormal Modes (QNMs)
approach. In order to find the QNMs corresponding to a black hole geometry, we
consider perturbations described by a massive scalar field non-minimally
coupled to gravity. We find that the QNM's frequencies turn out to be pure
imaginary leading to purely damped modes, that is in agreement with the
literature of dilatonic black holes. Our result exhibits the unstable behavior
of the considered geometry against the scalar perturbations. We consider both
the minimal coupling case, i.e., for which the coupling parameter
vanishes, and the case .Comment: sevarl changes, some reference was added, 10 pages, 4 figure
Relativistic magnetohydrodynamics in one dimension
We derive a number of solution for one-dimensional dynamics of relativistic
magnetized plasma that can be used as benchmark estimates in relativistic
hydrodynamic and magnetohydrodynamic numerical codes.
First, we analyze the properties of simple waves of fast modes propagating
orthogonally to the magnetic field in relativistically hot plasma. The magnetic
and kinetic pressures obey different equations of state, so that the system
behaves as a mixture of gases with different polytropic indices. We find the
self-similar solutions for the expansion of hot strongly magnetized plasma into
vacuum.
Second, we derive linear hodograph and Darboux equations for the relativistic
Khalatnikov potential, which describe arbitrary one-dimensional isentropic
relativistic motion of cold magnetized plasma and find their general and
particular solutions. The obtained hodograph and Darboux equations are very
powerful: system of highly non-linear, relativistic, time dependent equations
describing arbitrary (not necessarily self-similar) dynamics of highly
magnetized plasma reduces to a single linear differential equation.Comment: accepted by Phys. Rev.
Light Gravitinos at Colliders and Implications for Cosmology
Light gravitinos, with mass in the eV to MeV range, are well-motivated in
particle physics, but their status as dark-matter candidates is muddled by
early-Universe uncertainties. We investigate how upcoming data from colliders
may clarify this picture. Light gravitinos are produced primarily in the decays
of the next-to-lightest supersymmetric particle, resulting in spectacular
signals, including di-photons, delayed and non-pointing photons, kinked charged
tracks, and heavy metastable charged particles. We find that the Tevatron with
20/fb and the 7 TeV LHC with 1/fb may both see evidence for hundreds of
light-gravitino events. Remarkably, this collider data is also well suited to
distinguish between currently viable light-gravitino scenarios, with striking
implications for structure formation, inflation, and other early-Universe
cosmology.Comment: 12 pages, 6 figures. To be submitted to Phys. Rev. D
Alternative Bait Marker Systems for White-Tailed Deer
We compared alternative bait markers for a study of free-ranging white-tailed deer (Odocoileus virginianus) based on the following criteria: 1) detectability in fecal matter; 2) incorporation into corn bait; 3) palatability; and 4) cost. We used penned sheep (Ovis aries) as an experimental model to evaluate Microtaggants, metallic flakes, plastic chips, and rare earth elements as bait markers, and molasses and soy lecithin as marker adhesives. The metallic flakeÂ-soy lecithin combination best met our criteria. It was also successful in a field study evaluating supplemental feeding on deer behavior and activity in central Wisconsin. Metallic flakes were easily detected under field conditions, readily adhered to shelled corn bait, enabled assessment of deer activity at distinct feeding sites and could be used in studies of feeding behavior and movements of other free-ranging herbivores
Smooth tail index estimation
Both parametric distribution functions appearing in extreme value theory -
the generalized extreme value distribution and the generalized Pareto
distribution - have log-concave densities if the extreme value index gamma is
in [-1,0]. Replacing the order statistics in tail index estimators by their
corresponding quantiles from the distribution function that is based on the
estimated log-concave density leads to novel smooth quantile and tail index
estimators. These new estimators aim at estimating the tail index especially in
small samples. Acting as a smoother of the empirical distribution function, the
log-concave distribution function estimator reduces estimation variability to a
much greater extent than it introduces bias. As a consequence, Monte Carlo
simulations demonstrate that the smoothed version of the estimators are well
superior to their non-smoothed counterparts, in terms of mean squared error.Comment: 17 pages, 5 figures. Slightly changed Pickand's estimator, added some
more introduction and discussio
Renormalization-Scale Invariance, Minimal Sensitivity, and the Inclusive Hadronic Decays of a 115 GeV Higgs Particle
Known perturbative expressions for the decay rates of 115 GeV Higgs particle
into either two gluons or a pair are shown to exhibit
renormalization-scale-()-dependence that is largely removed via
renormalization-group/Pade-approximant estimates of these rates' next order
contributions. The extrema in characterizing both rates, as determined
from fully-known orders of perturbation theory, are very nearly equal to
corresponding -insensitive rates obtained via estimation of their next
order contributions, consistent with "minimal-sensitivity" expectations.Comment: 12 pages, 3 figures, LaTe
Exploring fraud and abuse in National Health Insurance Scheme (NHIS) using data mining technique as a statistical model
This study explored patterns of fraud and abuse that exist in the National Health Insurance Scheme (NHIS) claims in the Awutu-Effutu-Senya District using data mining techniques, with a specific focus on malaria-related claims. The study employed quantitative research approach with survey design as a strategy of enquiry. This survey explores the utility of various data mining techniques such as data collection, data cleaning/extraction, data integration, data selection, data transformation and pattern evaluation in the health domain. Samples of 720 clients diagnosed with malaria in the years 2013, 2014 and 2015 from 4 NHIS service providers in the districts were randomly selected for this study. Results from two-way between-subjects Analysis of Variance (ANOVA) revealed that Hospital B Private and Hospital A Private recorded the highest and lowest mean cost of malaria treatment respectively. The study further revealed that repetition of NHIS registration number, overbilling of drugs, drug mismatch, excessive prescription of drugs for malaria treatment and duplication of clients records were some of the fraud and abuse at the facility
Dear Wife : the Civil War letters of Chester K. Leach
Occasional paper (University of Vermont. Center for Research on Vermont) ; no. 20
Tunable and Multifunctional Eukaryotic Transcription Factors Based on CRISPR/Cas
Transcriptional regulation is central to the complex behavior of natural biological systems and synthetic gene circuits. Platforms for the scalable, tunable, and simple modulation of transcription would enable new abilities to study natural systems and implement artificial capabilities in living cells. Previous approaches to synthetic transcriptional regulation have relied on engineering DNA-binding proteins, which necessitate multistep processes for construction and optimization of function. Here, we show that the CRISPR/Cas system of Streptococcus pyogenes can be programmed to direct both activation and repression to natural and artificial eukaryotic promoters through the simple engineering of guide RNAs with base-pairing complementarity to target DNA sites. We demonstrate that the activity of CRISPR-based transcription factors (crisprTFs) can be tuned by directing multiple crisprTFs to different positions in natural promoters and by arraying multiple crisprTF-binding sites in the context of synthetic promoters in yeast and human cells. Furthermore, externally controllable regulatory modules can be engineered by layering gRNAs with small molecule-responsive proteins. Additionally, single nucleotide substitutions within promoters are sufficient to render them orthogonal with respect to the same gRNA-guided crisprTF. We envision that CRISPR-based eukaryotic gene regulation will enable the facile construction of scalable synthetic gene circuits and open up new approaches for mapping natural gene networks and their effects on complex cellular phenotypes
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