10,587 research outputs found
A Galaxy Photometric Redshift Catalog for the Sloan Digital Sky Survey Data Release 6
We present and describe a catalog of galaxy photometric redshifts (photo-z's)
for the Sloan Digital Sky Survey (SDSS) Data Release 6 (DR6). We use the
Artificial Neural Network (ANN) technique to calculate photo-z's and the
Nearest Neighbor Error (NNE) method to estimate photo-z errors for ~ 77 million
objects classified as galaxies in DR6 with r < 22. The photo-z and photo-z
error estimators are trained and validated on a sample of ~ 640,000 galaxies
that have SDSS photometry and spectroscopic redshifts measured by SDSS, 2SLAQ,
CFRS, CNOC2, TKRS, DEEP, and DEEP2. For the two best ANN methods we have tried,
we find that 68% of the galaxies in the validation set have a photo-z error
smaller than sigma_{68} =0.021 or $0.024. After presenting our results and
quality tests, we provide a short guide for users accessing the public data.Comment: 16 pages, 12 figure
On Combining Lensing Shear Information from Multiple Filters
We consider the possible gain in the measurement of lensing shear from
imaging data in multiple filters. Galaxy shapes may differ significantly across
filters, so that the same galaxy offers multiple samples of the shear. On the
other extreme, if galaxy shapes are identical in different filters, one can
combine them to improve the signal-to-noise and thus increase the effective
number density of faint, high redshift galaxies. We use the GOODS dataset to
test these scenarios by calculating the covariance matrix of galaxy
ellipticities in four visual filters (B,V,i,z). We find that galaxy shapes are
highly correlated, and estimate the gain in galaxy number density by combining
their shapes.Comment: 8 pages, no figures, submitted to JCA
Potency of Current Levothyroxine Preparations Evaluated by High-Performance Liquid Chromatography
Ten different levothyroxine products manufactured by six companies were analyzed by high-performance liquid chromatography. Although nine products met the United States Pharmacopeia requirements, one product was found to have only 47% of expected potency. Until these products become more uniform, we would not recommend interchangeability of levothyroxine preparations
Base heating methodology improvements, volume 1
This document is the final report for NASA MSFC Contract NAS8-38141. The contracted effort had the broad objective of improving the launch vehicles ascent base heating methodology to improve and simplify the determination of that environment for Advanced Launch System (ALS) concepts. It was pursued as an Advanced Development Plan (ADP) for the Joint DoD/NASA ALS program office with project management assigned to NASA/MSFC. The original study was to be completed in 26 months beginning Sep. 1989. Because of several program changes and emphasis on evolving launch vehicle concepts, the period of performance was extended to the current completion date of Nov. 1992. A computer code incorporating the methodology improvements into a quick prediction tool was developed and is operational for basic configuration and propulsion concepts. The code and its users guide are also provided as part of the contract documentation. Background information describing the specific objectives, limitations, and goals of the contract is summarized. A brief chronology of the ALS/NLS program history is also presented to provide the reader with an overview of the many variables influencing the development of the code over the past three years
Conformal symmetry and light flavor baryon spectra
The degeneracy among parity pairs systematically observed in the N and Delta
spectra is interpreted to hint on a possible conformal symmetry realization in
the light flavor baryon sector in line with AdS_5/CFT_4. The case is made by
showing that all the observed N and Delta resonances with masses below 2500 MeV
distribute fairly well each over the first levels of a unitary representation
of the conformal group, a representation that covers the spectrum of a
quark-diquark system, placed directly on the AdS_5 cone, conformally
compactified to R^1*S^3. The free geodesic motion on the S^3 manifold is
described by means of the scalar conformal equation there, which is of the
Klein-Gordon type. The equation is then gauged by the "curved" Coulomb
potential that has the form of a cotangent function. Conformal symmetry is not
exact, this because the gauge potential slightly modifies the conformal
centrifugal barrier of the free geodesic motion. Thanks to this, the degeneracy
between P11-S11 pairs from same level is relaxed, while the remaining states
belonging to same level remain practically degenerate. The model describes the
correct mass ordering in the P11-S11 pairs through the nucleon spectrum as a
combined effect of the above conformal symmetry breaking, on the one side, and
a parity change of the diquark from a scalar at low masses, to a pseudoscalar
at higher masses, on the other. The quality of the wave functions is
illustrated by calculations of realistic mean-square charge radii and electric
charge form-factors on the examples of the proton, and the protonic P11(1440),
and S11(1535) resonances. The scheme also allows for a prediction of the
dressing function of an effective instantaneous gluon propagator from the
Fourier transform of the gauge potential. We find a dressing function that is
finite in the infrared and tends to zero at infinity.Comment: Latex, 5 figures, 2 tables; Paper upgraded in accord with the
published version. Discussion on the meson sector include
The L_X--M relation of Clusters of Galaxies
We present a new measurement of the scaling relation between X-ray luminosity
and total mass for 17,000 galaxy clusters in the maxBCG cluster sample.
Stacking sub-samples within fixed ranges of optical richness, N_200, we measure
the mean 0.1-2.4 keV X-ray luminosity, , from the ROSAT All-Sky Survey.
The mean mass, , is measured from weak gravitational lensing of SDSS
background galaxies (Johnston et al. 2007). For 9 <= N_200 < 200, the data are
well fit by a power-law, /10^42 h^-2 erg/s = (12.6+1.4-1.3 (stat) +/- 1.6
(sys)) (/10^14 h^-1 M_sun)^1.65+/-0.13. The slope agrees to within 10%
with previous estimates based on X-ray selected catalogs, implying that the
covariance in L_X and N_200 at fixed halo mass is not large. The luminosity
intercent is 30%, or 2\sigma, lower than determined from the X-ray flux-limited
sample of Reiprich & Bohringer (2002), assuming hydrostatic equilibrium. This
difference could arise from a combination of Malmquist bias and/or systematic
error in hydrostatic mass estimates, both of which are expected. The intercept
agrees with that derived by Stanek et al. (2006) using a model for the
statistical correspondence between clusters and halos in a WMAP3 cosmology with
power spectrum normalization sigma_8 = 0.85. Similar exercises applied to
future data sets will allow constraints on the covariance among optical and hot
gas properties of clusters at fixed mass.Comment: 5 pages, 1 figure, MNRAS accepte
Endomyocardial Biopsy of Right Atrial Angiosarcoma Guided by Intracardiac Echocardiography
We report a case of a 22-year-old female who presented with pericardial effusion and cardiac tamponade. She was diagnosed with a right atrial mass by computed tomography and was referred to our institution for biopsy of this mass. Transcatheter biopsy was performed with intracardiac echocardiography (ICE) guidance, avoiding the need for transesophageal echocardiography or surgery to obtain the biopsy. ICE for transcatheter biopsy of an intracardiac mass is an attractive modality which provides precise localization of the cardiac structures
Trajectories and Particle Creation and Annihilation in Quantum Field Theory
We develop a theory based on Bohmian mechanics in which particle world lines
can begin and end. Such a theory provides a realist description of creation and
annihilation events and thus a further step towards a "beable-based"
formulation of quantum field theory, as opposed to the usual "observable-based"
formulation which is plagued by the conceptual difficulties--like the
measurement problem--of quantum mechanics.Comment: 11 pages LaTeX, no figures; v2: references added and update
Cross-correlation Weak Lensing of SDSS galaxy Clusters II: Cluster Density Profiles and the Mass--Richness Relation
We interpret and model the statistical weak lensing measurements around
130,000 groups and clusters of galaxies in the Sloan Digital Sky Survey
presented by Sheldon et al. 2007 (Paper I). We present non-parametric
inversions of the 2D shear profiles to the mean 3D cluster density and mass
profiles in bins of both optical richness and cluster i-band luminosity. We
correct the inferred 3D profiles for systematic effects, including non-linear
shear and the fact that cluster halos are not all precisely centered on their
brightest galaxies. We also model the measured cluster shear profile as a sum
of contributions from the brightest central galaxy, the cluster dark matter
halo, and neighboring halos. We infer the relations between mean cluster virial
mass and optical richness and luminosity over two orders of magnitude in
cluster mass; the virial mass at fixed richness or luminosity is determined
with a precision of 13% including both statistical and systematic errors. We
also constrain the halo concentration parameter and halo bias as a function of
cluster mass; both are in good agreement with predictions of LCDM models. The
methods employed here will be applicable to deeper, wide-area optical surveys
that aim to constrain the nature of the dark energy, such as the Dark Energy
Survey, the Large Synoptic Survey Telescope and space-based surveys
- …