4,762 research outputs found
Polyharmonic approximation on the sphere
The purpose of this article is to provide new error estimates for a popular
type of SBF approximation on the sphere: approximating by linear combinations
of Green's functions of polyharmonic differential operators. We show that the
approximation order for this kind of approximation is for
functions having smoothness (for up to the order of the
underlying differential operator, just as in univariate spline theory). This is
an improvement over previous error estimates, which penalized the approximation
order when measuring error in , p>2 and held only in a restrictive setting
when measuring error in , p<2.Comment: 16 pages; revised version; to appear in Constr. Appro
The Marshall Space Flight Center Development of Mirror Modules for the ART-XC Instrument aboard the Spectrum-Roentgen-Gamma Mission
The Marshall Space Flight Center (MSFC) is developing x-ray mirror modules for the ART-XC instrument on board the Spectrum-Roentgen Gamma Mission under a Reimbursable Agreement between NASA and the Russian Space Research Institute (IKI.) ART-XC will consist of seven co-aligned x-ray mirror modules with seven corresponding CdTe focal plane detectors. Currently, four of the modules are being fabricated by the Marshall Space Flight Center (MSFC.) Each MSFC module consist of 28 nested Ni/Co thin shells giving an effective area of 65 sq cm at 8 keV, response out to 30 keV, and an angular resolution of 45 arcsec or better HPD. Delivery of these modules to the IKI is scheduled for summer 2013. We present a status of the ART x-ray modules development at the MSFC
Tensile Fracture of Welded Polymer Interfaces: Miscibility, Entanglements and Crazing
Large-scale molecular simulations are performed to investigate tensile
failure of polymer interfaces as a function of welding time . Changes in the
tensile stress, mode of failure and interfacial fracture energy are
correlated to changes in the interfacial entanglements as determined from
Primitive Path Analysis. Bulk polymers fail through craze formation, followed
by craze breakdown through chain scission. At small welded interfaces are
not strong enough to support craze formation and fail at small strains through
chain pullout at the interface. Once chains have formed an average of about one
entanglement across the interface, a stable craze is formed throughout the
sample. The failure stress of the craze rises with welding time and the mode of
craze breakdown changes from chain pullout to chain scission as the interface
approaches bulk strength. The interfacial fracture energy is calculated
by coupling the simulation results to a continuum fracture mechanics model. As
in experiment, increases as before saturating at the average
bulk fracture energy . As in previous simulations of shear strength,
saturation coincides with the recovery of the bulk entanglement density. Before
saturation, is proportional to the areal density of interfacial
entanglements. Immiscibiltiy limits interdiffusion and thus suppresses
entanglements at the interface. Even small degrees of immisciblity reduce
interfacial entanglements enough that failure occurs by chain pullout and
Retrospective study of treatment outcome for individuals with aphasia
Measurement of outcomes subsequent to treatment and documentation of the efficiency with which outcomes are achieved is critical information for healthcare policy makers and third-party payers. This study employed the ASHA Functional Communication Measure (FCM) scales to retrospectively analyse charts of 20 aphasic patients. By discharge, both severe and moderate groups gained a median (across modalities) of 1 FCM level. The severe group remained dependent for communication, while the moderately impaired group typically achieved independent communication levels. Efficiency (amount of FCM level gain relative to number of treatment sessions) was greater for the moderate group; average number of treatment sessions was 40 for the severe group and 22 for the moderate group
A Systematic Review of Music Therapy Practice and Outcomes with Acute Adult Psychiatric In-Patients
PMCID: PMC3732280This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
O(N) methods in electronic structure calculations
Linear scaling methods, or O(N) methods, have computational and memory
requirements which scale linearly with the number of atoms in the system, N, in
contrast to standard approaches which scale with the cube of the number of
atoms. These methods, which rely on the short-ranged nature of electronic
structure, will allow accurate, ab initio simulations of systems of
unprecedented size. The theory behind the locality of electronic structure is
described and related to physical properties of systems to be modelled, along
with a survey of recent developments in real-space methods which are important
for efficient use of high performance computers. The linear scaling methods
proposed to date can be divided into seven different areas, and the
applicability, efficiency and advantages of the methods proposed in these areas
is then discussed. The applications of linear scaling methods, as well as the
implementations available as computer programs, are considered. Finally, the
prospects for and the challenges facing linear scaling methods are discussed.Comment: 85 pages, 15 figures, 488 references. Resubmitted to Rep. Prog. Phys
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Late-Type Near-Contact Eclipsing Binary [HH97] FS Aur-79
The secondary photometric standard star #79 for the FS Aur field (Henden &
Honeycutt 1997) designated as [HH97] FS Aur-79 (GSC 1874 399) is a short period
(0.2508 days) eclipsing binary whose light curve is a combination of the
Lyr and BY Dra type variables. High signal-to-noise multi-color
photometry were obtained using the USNO 1-m telescope. These light curves show
asymmetry at quadrature phases (O'Connell effect), which can be modeled with
the presence of star spots. A low resolution spectrum obtained with the 3.5-m
WIYN telescope at orbital phase 0.76 is consistent with a spectral type of dK7e
and dM3e. A radial velocity curve for the primary star was constructed using
twenty-four high resolution spectra from the 9.2 m HET. Spectra show H-alpha
and H-beta in emission confirming chromospheric activity and possibly the
presence of circumstellar material. Binary star models that simultaneously fit
the U, B, V, R and RV curves are those with a primary star of mass 0.59+-0.02
Msun, temperature 4100+-25 K, mean radius of 0.67 Rsun, just filling its Roche
lobe and a secondary star of mass 0.31+-0.09 Msun, temperature 3425+-25 K, mean
radius of 0.48 Rsun, just within its Roche lobe. An inclination angle of 83+-2
degrees with a center of mass separation of 1.62 Rsun is also derived. Star
spots, expected for a rotation period of less than a day, had to be included in
the modeling to fit the O'Connell effect
The Rest-frame Optical Colors of 99,000 SDSS Galaxies
We synthesize the rest-frame Stroemgren colors using SDSS spectra for 99,088
galaxies selected from Data Release 1. This narrow-band ~200 AA photometric
system (uz, vz, bz, yz), first designed for the determination of effective
temperature, metallicity and gravity of stars, measures the continuum spectral
slope of galaxies in the rest-frame 3200-5800 AA wavelength range. Galaxies
form a remarkably narrow locus (~0.03 mag) in the resulting color-color
diagram. The Bruzual & Charlot population synthesis models suggest that the
position of a galaxy along this locus is controlled by a degenerate combination
of metallicity and age of the dominant stellar population. Galaxy distribution
along the locus is bimodal, with the local minimum corresponding to an ~1 Gyr
old single stellar population. The position perpendicular to the locus is
independent of metallicity and age, and reflects the galaxy's dust content, as
implied by both the models and the statistics of IRAS detections. A comparison
of this locus with the galaxy locus in the H_delta-D_n(4000) diagram, utilized
by Kauffmann et al. (2003) to estimate stellar masses, reveals a tight
correlation, although the two analyzed spectral ranges barely overlap. Overall,
the galaxy spectral energy distribution in the entire UV to near-IR range can
be described as a single-parameter family with an accuracy of 0.1 mag, or
better. This nearly one-dimensional distribution of galaxies in the
multi-dimensional space of measured parameters strongly supports the conclusion
of Yip et al. (2004), based on a principal component analysis, that SDSS galaxy
spectra can be described by a small number of eigenspectra. Apparently, the
contributions of stellar populations that dominate the optical emission from
galaxies are combined in a simple and well-defined way.Comment: Accepted for publication in MNRAS; 19 pages, 28 color figure
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