16,446 research outputs found
Improved Constraints on Cosmic Microwave Background Secondary Anisotropies from the Complete 2008 South Pole Telescope Data
We report measurements of the cosmic microwave background (CMB) power spectrum from the complete 2008 South Pole Telescope (SPT) data set. We analyze twice as much data as the first SPT power spectrum analysis, using an improved cosmological parameter estimator which fits multi-frequency models to the SPT 150 and 220 GHz bandpowers. We find an excellent fit to the measured bandpowers with a model that includes lensed primary CMB anisotropy, secondary thermal (tSZ) and kinetic (kSZ) Sunyaev-Zel'dovich anisotropies, unclustered synchrotron point sources, and clustered dusty point sources. In addition to measuring the power spectrum of dusty galaxies at high signal-to-noise, the data primarily constrain a linear combination of the kSZ and tSZ anisotropy contributions at 150 GHz and ℓ = 3000: D^(tSZ) ^(3000) + 0.5 D_(kSZ)^(3000) = 4.5 ± 1.0 μK^2. The 95% confidence upper limits on secondary anisotropy power are D ^(tSZ)_(3000) < 5.3 μK^2 and D^(kSZ)_(3000) < 6.5 μK^2. We also consider the potential correlation of dusty and tSZ sources and find it incapable of relaxing the tSZ upper limit. These results increase the significance of the lower than expected tSZ amplitude previously determined from SPT power spectrum measurements. We find that models including non-thermal pressure support in groups and clusters predict tSZ power in better agreement with the SPT data. Combining the tSZ power measurement with primary CMB data halves the statistical uncertainty on σ8. However, the preferred value of σ8 varies significantly between tSZ models. Improved constraints on cosmological parameters from tSZ power spectrum measurements require continued progress in the modeling of the tSZ power
A Risk-Adjusted Model for Ovarian Cancer Care and Disparities in Access to High-Performing Hospitals.
ObjectiveTo validate the observed/expected ratio for adherence to ovarian cancer treatment guidelines as a risk-adjusted measure of hospital quality care, and to identify patient characteristics associated with disparities in access to high-performing hospitals.MethodsThis was a retrospective population-based study of stage I-IV invasive epithelial ovarian cancer reported to the California Cancer Registry between 1996 and 2014. A fit logistic regression model, which was risk-adjusted for patient and disease characteristics, was used to calculate the observed/expected ratio for each hospital, stratified by hospital annual case volume. A Cox proportional hazards model was used for survival analyses, and a multivariable logistic regression model was used to identify independent predictors of access to high-performing hospitals.ResultsThe study population included 30,051 patients who were treated at 426 hospitals: low observed/expected ratio (n=304) 23.5% of cases; intermediate observed/expected ratio (n=92) 57.8% of cases; and high observed/expected ratio (n=30) 18.7% of cases. Hospitals with high observed/expected ratios were significantly more likely to deliver guideline-adherent care (53.3%), compared with hospitals with intermediate (37.8%) and low (27.5%) observed/expected ratios (P<.001). Median disease-specific survival time ranged from 73.0 months for hospitals with high observed/expected ratios to 48.1 months for hospitals with low observed/expected ratios (P<.001). Treatment at a hospital with a high observed/expected ratio was an independent predictor of superior survival compared with hospitals with intermediate (hazard ratio [HR] 1.06, 95% CI 1.01-1.11, P<.05) and low (HR 1.10, 95% CI 1.04-1.16, P<.001) observed/expected ratios. Being of Hispanic ethnicity (odds ratio [OR] 0.85, 95% CI 0.78-0.93, P<.001, compared with white), having Medicare insurance (OR 0.74, 95% CI 0.68-0.81 P<.001, compared with managed care), having a Charlson Comorbidity Index score of 2 or greater (OR 0.91, 95% CI 0.83-0.99, P<.05), and being of lower socioeconomic status (lowest quintile OR 0.41, 95% CI 0.36-0.46, P<.001, compared with highest quintile) were independent negative predictors of access to a hospital with a high observed/expected ratio.ConclusionOvarian cancer care at a hospital with a high observed/expected ratio is an independent predictor of improved survival. Barriers to high-performing hospitals disproportionately affect patients according to sociodemographic characteristics. Triage of patients with suspected ovarian cancer according to a performance-based observed/expected ratio hospital classification is a potential mechanism for expanded access to expert care
Chaos and Synchronized Chaos in an Earthquake Model
We show that chaos is present in the symmetric two-block Burridge-Knopoff
model for earthquakes. This is in contrast with previous numerical studies, but
in agreement with experimental results. In this system, we have found a rich
dynamical behavior with an unusual route to chaos. In the three-block system,
we see the appearance of synchronized chaos, showing that this concept can have
potential applications in the field of seismology.Comment: To appear in Physical Review Letters (13 pages, 6 figures
On the extra phase correction to the semiclassical spin coherent-state propagator
The problem of an origin of the Solary-Kochetov extra-phase contribution to
the naive semiclassical form of a generalized phase-space propagator is
addressed with the special reference to the su(2) spin case which is the most
important in applications. While the extra-phase correction to a flat
phase-space propagator can straightforwardly be shown to appear as a difference
between the principal and the Weyl symbols of a Hamiltonian in the
next-to-leading order expansion in the semiclassical parameter, the same
statement for the semiclassical spin coherent-state propagator holds provided
the Holstein-Primakoff representation of the su(2) algebra generators is
employed.Comment: 19 pages, no figures; a more general treatment is presented, some
references are added, title is slightly changed; submitted to JM
- …