678 research outputs found
Curvature of blended rolled edge reflectors at the shadow boundary contour
A technique is advanced for computing the radius of curvature of blended rolled edge reflector surfaces at the shadow boundary, in the plane perpendicular to the shadow boundary contour. This curvature must be known in order to compute the spurious endpoint contributions in the physical optics (PO) solution for the scattering from reflectors with rolled edges. The technique is applicable to reflectors with radially-defined rim-shapes and rolled edge terminations. The radius of curvature for several basic reflector systems is computed, and it is shown that this curvature can vary greatly along the shadow boundary contour. Finally, the total PO field in the target zone of a sample compact range system is computed and corrected using the shadow boundary radius of curvature, obtained using the technique. It is shown that the fields obtained are a better approximation to the true scattered fields
Most of the genetic covariation between major depressive and alcohol use disorders is explained by trait measures of negative emotionality and behavioral control
Background Mental health disorders commonly co-occur, even between conceptually distinct syndromes, such as internalizing and externalizing disorders. The current study investigated whether phenotypic, genetic, and environmental variance in negative emotionality and behavioral control account for the covariation between major depressive disorder (MDD) and alcohol use disorder (AUD). Method A total of 3623 members of a national twin registry were administered structured diagnostic telephone interviews that included assessments of lifetime histories of MDD and AUD, and were mailed self-report personality questionnaires that assessed stress reactivity (SR) and behavioral control (CON). A series of biometric models were fitted to partition the proportion of covariance between MDD and AUD into SR and CON. Results A statistically significant proportion of the correlation between MDD and AUD was due to variance specific to SR (men = 0.31, women = 0.27) and CON (men = 0.20, women = 0.19). Further, genetic factors explained a large proportion of this correlation (0.63), with unique environmental factors explaining the rest. SR explained a significant proportion of the genetic (0.33) and environmental (0.23) overlap between MDD and AUD. In contrast, variance specific to CON accounted for genetic overlap (0.32), but not environmental overlap (0.004). In total, SR and CON accounted for approximately 70% of the genetic and 20% of the environmental covariation between MDD and AUD. Conclusions This is the first study to demonstrate that negative emotionality and behavioral control confer risk for the co-occurrence of MDD and AUD via genetic factors. These findings are consistent with the aims of NIMH's RDoC proposal to elucidate how transdiagnostic risk factors drive psychopathology
Multiwavelength Mass Comparisons of the z~0.3 CNOC Cluster Sample
Results are presented from a detailed analysis of optical and X-ray
observations of moderate-redshift galaxy clusters from the Canadian Network for
Observational Cosmology (CNOC) subsample of the EMSS. The combination of
extensive optical and deep X-ray observations of these clusters make them ideal
candidates for multiwavelength mass comparison studies. X-ray surface
brightness profiles of 14 clusters with 0.17<z<0.55 are constructed from
Chandra observations and fit to single and double beta-models. Spatially
resolved temperature analysis is performed, indicating that five of the
clusters in this sample exhibit temperature gradients within their inner 60-200
kpc. Integrated spectra extracted within R_2500 provide temperature, abundance,
and luminosity information. Under assumptions of hydrostatic equilibrium and
spherical symmetry, we derive gas and total masses within R_2500 and R_200. We
find an average gas mass fraction within R_200 of 0.136 +/- 0.004, resulting in
Omega_m=0.28 +/- 0.01 (formal error). We also derive dynamical masses for these
clusters to R_200. We find no systematic bias between X-ray and dynamical
methods across the sample, with an average M(dyn)/M(X-ray) = 0.97 +/- 0.05. We
also compare X-ray masses to weak lensing mass estimates of a subset of our
sample, resulting in a weighted average of M(lens)/M(X-ray) of 0.99 +/- 0.07.
We investigate X-ray scaling relationships and find powerlaw slopes which are
slightly steeper than the predictions of self-similar models, with an E(z)^(-1)
Lx-Tx slope of 2.4 +/- 0.2 and an E(z) M_2500-Tx slope of 1.7 +/- 0.1.
Relationships between red-sequence optical richness (B_gc,red) and global
cluster X-ray properties (Tx, Lx and M_2500) are also examined and fitted.Comment: Astrophysical Journal, 48 pages, 11 figures, LaTeX. Added correction
to surface brightness normalization of MS1512.4+3647, corrections to sample
gas mass fractions and calculated value of Omega_m. Figure resolution has
been reduced to comply with astro-ph upload requirement
Quantitative MRI Measurement of Binder Distributions in Green-State Ceramics
Development of reliable and improved structural ceramics for advanced heat engines and other applications requires process diagnostics and materials evaluation from powder preparation to green-body forming to final sintering. Injection molding is a promising processing method being developed for mass production of complex-shaped heat engine components such as turbochargers (rotors and stator vanes) and engine valves. Major processing steps in injection-molded ceramic manufacturing include preparation of ceramic powders and organic binders, mixing, molding, binder removal, sintering, and finishing [1]. While materials evaluation and diagnostics are needed throughout the process, it is particularly important to evaluate the distributions of binders/plasticizers in as-molded green bodies [2]. Poor distribution of these organics in a green body can lead to a final part that is defective or that has poor mechanical properties after it is sintered
The LWA1 Radio Telescope
LWA1 is a new radio telescope operating in the frequency range 10-88 MHz,
located in central New Mexico. The telescope consists of 258 pairs of
dipole-type antennas whose outputs are individually digitized and formed into
beams. Simultaneously, signals from all dipoles can be recorded using one of
the instrument's "all dipoles" modes, facilitating all-sky imaging. Notable
features of the instrument include high intrinsic sensitivity (about 6 kJy
zenith system equivalent flux density), large instantaneous bandwidth (up to 78
MHz), and 4 independently-steerable beams utilizing digital "true time delay"
beamforming. This paper summarizes the design of LWA1 and its performance as
determined in commissioning experiments. We describe the method currently in
use for array calibration, and report on measurements of sensitivity and
beamwidth.Comment: 9 pages, 14 figures, accepted by IEEE Trans. Antennas & Propagation.
Various minor changes from previous versio
The Red-Sequence Luminosity Function in Galaxy Clusters since z~1
We use a statistical sample of ~500 rich clusters taken from 72 square
degrees of the Red-Sequence Cluster Survey (RCS-1) to study the evolution of
~30,000 red-sequence galaxies in clusters over the redshift range 0.35<z<0.95.
We construct red-sequence luminosity functions (RSLFs) for a well-defined,
homogeneously selected, richness limited sample. The RSLF at higher redshifts
shows a deficit of faint red galaxies (to M_V=> -19.7) with their numbers
increasing towards the present epoch. This is consistent with the `down-sizing`
picture in which star-formation ended at earlier times for the most massive
(luminous) galaxies and more recently for less massive (fainter) galaxies. We
observe a richness dependence to the down-sizing effect in the sense that, at a
given redshift, the drop-off of faint red galaxies is greater for poorer (less
massive) clusters, suggesting that star-formation ended earlier for galaxies in
more massive clusters. The decrease in faint red-sequence galaxies is
accompanied by an increase in faint blue galaxies, implying that the process
responsible for this evolution of faint galaxies is the termination of
star-formation, possibly with little or no need for merging. At the bright end,
we also see an increase in the number of blue galaxies with increasing
redshift, suggesting that termination of star-formation in higher mass galaxies
may also be an important formation mechanism for higher mass ellipticals. By
comparing with a low-redshift Abell Cluster sample, we find that the
down-sizing trend seen within RCS-1 has continued to the local universe.Comment: ApJ accepted. 11 pages, 5 figure
- …