3,554 research outputs found
A Frequentist Approach to Computer Model Calibration
This paper considers the computer model calibration problem and provides a
general frequentist solution. Under the proposed framework, the data model is
semi-parametric with a nonparametric discrepancy function which accounts for
any discrepancy between the physical reality and the computer model. In an
attempt to solve a fundamentally important (but often ignored) identifiability
issue between the computer model parameters and the discrepancy function, this
paper proposes a new and identifiable parametrization of the calibration
problem. It also develops a two-step procedure for estimating all the relevant
quantities under the new parameterization. This estimation procedure is shown
to enjoy excellent rates of convergence and can be straightforwardly
implemented with existing software. For uncertainty quantification,
bootstrapping is adopted to construct confidence regions for the quantities of
interest. The practical performance of the proposed methodology is illustrated
through simulation examples and an application to a computational fluid
dynamics model.Comment: 21 pages, 2 figure
Off Mass Shell Effects in Hadron Electric Dipole Moments
We note that off the quark mass shell the operators
and , both of which reduce to
in the non-relativistic limit, are no longer
identical. In this paper we explore the effects of this difference in the
contribution of these quark electric moments to hadronic electric moments.Comment: 21 pages, 1 figure, Revtex, uses psfi
K2-231 b: A sub-Neptune exoplanet transiting a solar twin in Ruprecht 147
We identify a sub-Neptune exoplanet ( R)
transiting a solar twin in the Ruprecht 147 star cluster (3 Gyr, 300 pc, [Fe/H]
= +0.1 dex). The ~81 day light curve for EPIC 219800881 (V = 12.71) from K2
Campaign 7 shows six transits with a period of 13.84 days, a depth of ~0.06%,
and a duration of ~4 hours. Based on our analysis of high-resolution MIKE
spectra, broadband optical and NIR photometry, the cluster parallax and
interstellar reddening, and isochrone models from PARSEC, Dartmouth, and MIST,
we estimate the following properties for the host star: M, R, and K. This star appears to be single, based on our modeling of the
photometry, the low radial velocity variability measured over nearly ten years,
and Keck/NIRC2 adaptive optics imaging and aperture-masking interferometry.
Applying a probabilistic mass-radius relation, we estimate that the mass of
this planet is M, which would cause a RV
semi-amplitude of m s that may be measurable with existing
precise RV facilities. After statistically validating this planet with BLENDER,
we now designate it K2-231 b, making it the second sub-stellar object to be
discovered in Ruprecht 147 and the first planet; it joins the small but growing
ranks of 23 other planets found in open clusters.Comment: 24 pages, 7 figures, light curve included as separate fil
Atmospheric Circulation of Hot Jupiters: Three-dimensional circulation models of HD 209458b and HD 189733b with Simplified Forcing
We present global, three-dimensional numerical simulations of the atmospheric
circulation on HD 209458b and HD 189733b and calculate the infrared spectra and
light curves predicted by these simulations, which we compare with available
observations. Radiative heating/cooling is parameterized with a simplified
Newtonian relaxation scheme. Our simulations develop day-night temperature
contrasts that vary strongly with pressure. At low pressure (<10 mbar), air
flows from the substellar point toward the antistellar point, both along the
equator and over the poles. At deeper levels, the flow develops an eastward
equatorial jet with speeds of 3-4 km/sec, with weaker westward flows at high
latitudes. This basic flow pattern is robust to variations in model resolution,
gravity, radiative time constant, and initial temperature structure. Nightside
spectra show deep absorption bands of H2O, CO, and/or CH4, whereas on the
dayside these absorption bands flatten out or even flip into emission. This
results from the strong effect of dynamics on the vertical temperature-pressure
structure; the temperature decreases strongly with altitude on the nightside
but becomes almost isothermal on the dayside. In Spitzer bandpasses, our
predicted planet-to-star flux ratios vary by a factor of 2-10 with orbital
phase, depending on the wavelength and chemistry. For HD 189733b, where a
detailed 8-micron light curve has been obtained, we correctly produce the
observed phase offset of the flux maximum, but we do not explain the flux
minimum and we overpredict the total flux variation. This discrepancy likely
results from the simplifications inherent in the Newtonian relaxation scheme
and provides motivation for incorporating realistic radiative transfer in
future studies.Comment: 17 pages, 14 figures, submitted for publication in Ap
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Gene-expression analysis of clozapine treatment in whole blood of patients with psychosis
OBJECTIVES: Clozapine is an atypical antipsychotic primarily prescribed for treatment-resistant schizophrenia. We tested the specific effect of clozapine versus other drug treatments on whole-blood gene expression in a sample of patients with psychosis from the UK.
METHODS: A total of 186 baseline whole-blood samples from individuals receiving treatment for established psychosis were analysed for gene expression on Illumina HumanHT-12.v4 BeadChips. After standard quality-control procedures, 152 samples remained, including 55 from individuals receiving clozapine. In a within-case study design, weighted gene correlation network analysis was used to identify modules of coexpressed genes. The influence of mood stabilizers, lithium carbonate/lithium citrate and sodium valproate was studied to identify their possible roles as confounders.
RESULTS: Individuals receiving clozapine as their only antipsychotic (clozapine monotherapy) had a nominal association with one gene-expression module, whereas no significant change in gene expression was found for other drugs.
CONCLUSION: Overall, this study does not provide evidence that clozapine treatment induces medium to large different gene-expression patterns in human whole blood versus other antipsychotic treatments. This does not rule out the possibility of smaller effects as observed for other common antipsychotic treatments
Productivity enhancement of aircraft turbine disk using a two-step strategy based on tool-path planning and NC-code optimization
Most of the parts of an aircraft require the use of lightweight and high-strength materials. Since aircraft parts mainly use mechanical cutting processes, which are the most suitable material removal mechanism, to minimize changes in material properties, it is necessary to develop an optimal cutting tool and cutting solution for each material. This work aims to enhance productivity and reduce the production cost of an aircraft turbine disk through designing a cutting strategy and optimizing the cutting conditions using a simulation approach. The number of tools was reduced from eight to six compared to the existing process conditions for semi-finishing and finishing of a turbine disk, and a new tool path was proposed through simulation. The cycle time was reduced by about 24%. NC-code optimization was performed through feed-rate optimization considering cutting force and chip thickness. As a result, cycle times were reduced by about 14%. Through tool-path optimization and NC-code optimization, it was confirmed that the total cycle time was reduced by about 54%, and tool wear was significantly improved
A Warp in Progress : H I and Radio Continuum Observations of the Spiral NGC 3145
Date of Acceptance: 16/06/2015We present VLA H I and 6 cm radio continuum observations of the spiral NGC 3145 and H I observations of its two companions, NGC 3143 and PGC 029578. In optical images NGC 3145 has stellar arms that appear to cross, forming "X"-features. Our radio continuum observations rule out shock fronts at 3 of the 4 "X"-features. In the middle-to-outer disk, the H I line-profiles of NGC 3145 are skewed. Relative to the disk, the gas in the skewed wing of the line-profiles has z-motions away from us on the approaching side of the galaxy and z-motions of about the same magnitude (about 40 km/s) towards us on the receding side. These warping motions imply that there has been a perturbation with a sizeable component perpendicular to the disk over large spatial scales. Two features in NGC 3145 have velocities indicating that they are out-of-plane tidal arms. One is an apparent branch of a main spiral arm; the velocity of the branch is 150 km/s greater than the spiral arm where they appear to intersect in projection. The other is an arm that forms 3 of the "X"-features. It differs in velocity by 56 km/s from the disk at the same projected location. Based on its SFR and H I properties, NGC 3143 is the more likely of the two companions to have interacted with NGC 3145 recently. A simple analytic model demonstrates that an encounter between NGC 3143 and NGC 3145 is a plausible explanation for the observed warping motions in NGC 3145.Peer reviewe
2+1 Dimensional QED and a Novel Phase Transition
We investigate the chiral phase transition in 2+1 dimensional QED. Previous
gap equation and lattice Monte-Carlo studies of symmetry breaking have found
that symmetry breaking ceases to occur when the number of fermion flavors
exceeds a critical value. Here we focus on the order of the transition. We find
that there are no light scalar degrees of freedom present as the critical
number of flavors is approached from above (in the symmetric phase). Thus the
phase transition is not second order, rendering irrelevant the renormalization
group arguments for a fluctuation induced transition. However, the order
parameter vanishes continuously in the broken phase, so this transition is also
unlike a conventional first order phase transition.Comment: 11 pages, Late
Unitarity, BRST Symmetry and Ward Identities in Orbifold Gauge Theories
We discuss the use of BRST symmetry and the resulting Ward identities for
orbifold gauge theories as consistency checks in an arbitrary number of
dimensions. We verify that both the usual orbifold symmetry breaking and the
recently proposed Higgsless symmetry breaking are consistent with the
nilpotency of the BRST transformation. Imposing the Ward identities resulting
from the BRST symmetry on the 4-point functions of theory, we obtain relations
on the coupling constants that are shown to be equivalent to the conditions for
tree level unitarity. We present the complete set of these sum rules also for
inelastic scattering and discuss applications to 6-dimensional models and to
incomplete matter multiplets on orbifold fixed points.Comment: 34 pages, LaTeX (feynmf.sty, url.sty and thophys.sty included),
v2:references added, v3:typos corrected, sec.3 revise
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