We present an improved analysis of halo substructure traced by RR Lyrae stars in the Sloan Digital Sky Survey (SDSS) stripe 82 region. With the addition of SDSS-II data, a revised selection method ...based on new ugriz light curve templates results in a sample of 483 RR Lyrae stars that is essentially free of contamination. The main result from our first study persists: the spatial distribution of halo stars at galactocentric distances 5-100 kpc is highly inhomogeneous. At least 20% of halo stars within 30 kpc from the Galactic center can be statistically associated with substructure. We present strong direct evidence, based on both RR Lyrae stars and main-sequence stars, that the halo stellar number density profile significantly steepens beyond a Galactocentric distance of ~30 kpc, and a larger fraction of the stars are associated with substructure. By using a novel method that simultaneously combines data for RR Lyrae and main-sequence stars, and using photometric metallicity estimates for main-sequence stars derived from deep co-added u-band data, we measure the metallicity of the Sagittarius dSph tidal stream (trailing arm) toward R.A. ~2h-3h and decl. ~ 0 deg to be 0.3 dex higher (Fe/H = -1.2) than that of surrounding halo field stars. Together with a similar result for another major halo substructure, the Monoceros stream, these results support theoretical predictions that an early forming, smooth inner halo, is metal-poor compared to high surface brightness material that have been accreted onto a later-forming outer halo. The mean metallicity of stars in the outer halo that are not associated with detectable clumps may still be more metal-poor than the bulk of inner-halo stars, as has been argued from other data sets.
Background:
American football players have an increased level of risk for hip injuries because of the high level of contact, biomechanical load, and anatomic strain placed on the hip joint. Many ...injuries are attributed to soft tissue injury rather than intra-articular lesions. However, because of improved imaging and increased knowledge, physicians are attributing unexplained hip pain to intra-articular lesions with increasing frequency.
Purpose:
To assess the prevalence of pathologic intra-articular hip lesions in a younger, retired National Football League (NFL) player cohort evaluated for persistent hip pain.
Study Design:
Case series; Level of evidence, 4.
Methods:
A retrospective chart review was performed of magnetic resonance imaging (MRI) on retired NFL players evaluated at an orthopaedic clinic for persistent hip pain. All MRIs were performed at the same location and reviewed by the same independent radiologist. The study included 62 hips; MRI was used to evaluate 27 hips, and MRI arthrogram was used to evaluate 35 hips. Images were assessed for labral tears, chondral lesions, ligamentum teres (LT) tears, bone cysts, osteophytes, loose bodies, trochanteric bursitis, and alpha angle. Player demographics, including position and seasons played, were recorded.
Results:
From February 2011 to December 2012, a total of 50 retired players from the NFL (average age, 33 years; range, 27-39 years) received impairment evaluations assessing all symptomatic joints. Thirty-eight (76%) players had hip complaints and underwent a dedicated hip MRI. Twenty-four players (63%) had bilateral hip pain, for a total of 62 hips evaluated. There were 55 (89%) labral tears, 61 (98%) chondral lesions, and 50 (81%) partial or complete LT tears identified on MRI. Additional findings included 3 (5%) hips with osteophytes, 9 (14.5%) with subchondral bone cysts, and 3 (5%) with paralabral cysts. None of the players were found to have trochanteric bursitis or loose bodies. Fifty-eight of 62 alpha angles could be measured, for a mean of 59° (range, 39°-77°). The majority of players were defensive players (63%), while the remainder were offensive players (34%) and 1 special teams player. Position breakdown was as follows: 29% were defensive backs, 16% played the defensive line, 18% were linebackers, 13% were fullbacks, 11% were wide receivers, 5% played the offensive line, and the remaining 8% were kickers, running backs, and quarterbacks.
Conclusion:
This study demonstrated a high incidence of intra-articular pathologic lesions of the hip in a younger cohort of retired NFL players. The majority of players had bilateral hip pain. The most common finding was chondral lesions, followed by labral tears. Future research is needed to further elucidate incidence and treatment outcomes using prospective studies examining active and retired players with hip-related injuries.
Abstract Purpose Percutaneous endoscopic gastrostomy (PEG) tube placement is a common procedure performed for children with oral aspiration and failure to thrive. The concurrent presence of ...gastroesophageal reflux (GER) may be difficult to diagnose in these children and may dictate the need for an antireflux procedure. The purpose of this study was to review our preoperative evaluation of children undergoing PEG placement to better elucidate preoperative factors that may require eventual fundoplication. Methods A retrospective review at a tertiary care, children's hospital between May 2002 and August 2007 was performed of patients undergoing PEG placement. Patients were identified through database search by operative procedure codes. Patient groups were defined as those undergoing PEG alone (group 1) and those requiring fundoplication after prior PEG (group 2). Comparison of patient demographics and radiologic qualitative results of GER was analyzed using χ2 analysis, with significance determined at P < .05. Results A total of 863 patients underwent PEG placement over this 64-month period. A sampled cohort of patients undergoing PEG over a year comprised group 1. Forty-four patients (5.1%) underwent Nissen fundoplication after prior PEG placement (group 2). Patient demographics were similar between the groups. Comparison of comorbid conditions and qualitative indicators of GER between the groups showed only cerebral palsy had a significantly higher associated risk of GER that required antireflux surgery. Preoperative clinical assessment had a 95% positive predictive value in identifying children who required only PEG. Conclusions Despite the high predictive value of individualized clinical assessment in the ultimate decision for gastrostomy without need of fundoplication, further studies are needed to determine whether children with conditions such as cerebral palsy may require a concurrent antireflux surgery at the time of gastrostomy.
We quantify the variability of faint unresolved optical sources using a catalog based on multiple SDSS imaging observations. The catalog covers SDSS stripe 82, which lies along the celestial equator ...in the southern Galactic hemisphere (22h24m < aJ2000.0 < 04h08m, -1.27° < dJ2000.0 < +1.27°, ~290 deg2), and contains 34 million photometric observations in the SDSS ugriz system for 748,084 unresolved sources at high Galactic latitudes (b < -20°) that were observed at least four times in each of the ugri bands (with a median of 10 observations obtained over ~6 yr). In each photometric bandpass we compute various low-order light-curve statistics, such as rms scatter, y2 per degree of freedom, skewness, and minimum and maximum magnitude, and use them to select and study variable sources. We find that 2% of unresolved optical sources brighter than g = 20.5 appear variable at the 0.05 mag level (rms) simultaneously in the g and r bands (at high Galactic latitudes). The majority (2 out of 3) of these variable sources are low-redshift (<2) quasars, although they represent only 2% of all sources in the adopted flux-limited sample. We find that at least 90% of quasars are variable at the 0.03 mag level (rms) and confirm that variability is as good a method for finding low-redshift quasars as the UV excess color selection (at high Galactic latitudes). We analyze the distribution of light-curve skewness for quasars and find that it is centered on zero. We find that about one-fourth of the variable stars are RR Lyrae stars, and that only 0.5% of stars from the main stellar locus are variable at the 0.05 mag level. The distribution of light-curve skewness in the g - r versus u - g color-color diagram on the main stellar locus is found to be bimodal (with one mode consistent with Algol-like behavior). Using over 600 RR Lyrae stars, we demonstrate rich halo substructure out to distances of 100 kpc. We extrapolate these results to the expected performance by the Large Synoptic Survey Telescope and estimate that it will obtain well-sampled, 2% accurate, multicolor light curves for ~2 million low-redshift quasars and discover at least 50 million variable stars.
An insider's view of the U.S. government's response to the 2007-2009 global financial crisis, as recounted by the people who made the key decisions In 2008, the world's financial system stood on the ...brink of disaster. The United States faced an unprecedented crisis when the investment bank Lehman Brothers collapsed, setting off a global panic. Faced with the prospect of a new Great Depression, the Treasury Department, the Federal Reserve, the Federal Deposit Insurance Corporation, and other agencies took extraordinary measures to contain the damage and steady the financial system and the economy. Edited by three of the policymakers who led the government's response to the crisis, with chapters written by the teams tasked with finding policy solutions, this book provides a comprehensive accounting of the internal debates and controversies surrounding the measures that were taken to stabilize the financial system and the economy. Offering previously untold insight into the key choices (including rejected options) and a frank evaluation of successes and failures, this volume is both an important historical document and an indispensable guide for confronting future financial calamities.
We present an improved analysis of halo substructure traced by RR Lyrae stars in the SDSS stripe 82 region. With the addition of SDSS-II data, a revised selection method based on new ugriz light ...curve templates results in a sample of 483 RR Lyrae stars that is essentially free of contamination. The main result from our first study persists: the spatial distribution of halo stars at galactocentric distances 5--100 kpc is highly inhomogeneous. At least 20% of halo stars within 30 kpc from the Galactic center can be statistically associated with substructure. We present strong direct evidence, based on both RR Lyrae stars and main sequence stars, that the halo stellar number density profile significantly steepens beyond a Galactocentric distance of ~30 kpc, and a larger fraction of the stars are associated with substructure. By using a novel method that simultaneously combines data for RR Lyrae and main sequence stars, and using photometric metallicity estimates for main sequence stars derived from deep co-added u-band data, we measure the metallicity of the Sagittarius dSph tidal stream (trailing arm) towards R.A.2h-3h and Dec~0 deg to be 0.3 dex higher (Fe/H=-1.2) than that of surrounding halo field stars. Together with a similar result for another major halo substructure, the Monoceros stream, these results support theoretical predictions that an early forming, smooth inner halo, is metal poor compared to high surface brightness material that have been accreted onto a later-forming outer halo. The mean metallicity of stars in the outer halo that are not associated with detectable clumps may still be more metal-poor than the bulk of inner-halo stars, as has been argued from other data sets.
We quantify the variability of faint unresolved optical sources using a catalog based on multiple SDSS imaging observations. The catalog covers SDSS Stripe 82, and contains 58 million photometric ...observations in the SDSS ugriz system for 1.4 million unresolved sources. In each photometric bandpass we compute various low-order lightcurve statistics and use them to select and study variable sources. We find that 2% of unresolved optical sources brighter than g=20.5 appear variable at the 0.05 mag level (rms) simultaneously in the g and r bands. The majority (2/3) of these variable sources are low-redshift (<2) quasars, although they represent only 2% of all sources in the adopted flux-limited sample. We find that at least 90% of quasars are variable at the 0.03 mag level (rms) and confirm that variability is as good a method for finding low-redshift quasars as is the UV excess color selection (at high Galactic latitudes). We analyze the distribution of lightcurve skewness for quasars and find that is centered on zero. We find that about 1/4 of the variable stars are RR Lyrae stars, and that only 0.5% of stars from the main stellar locus are variable at the 0.05 mag level. The distribution of lightcurve skewness in the g-r vs. u-g color-color diagram on the main stellar locus is found to be bimodal (with one mode consistent with Algol-like behavior). Using over six hundred RR Lyrae stars, we demonstrate rich halo substructure out to distances of 100 kpc. We extrapolate these results to expected performance by the Large Synoptic Survey Telescope and estimate that it will obtain well-sampled 2% accurate, multi-color lightcurves for ~2 million low-redshift quasars, and will discover at least 50 million variable stars.
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