Causality in relativistic many body theory

The stability of the nuclear matter system with respect to density fluctuations is examined exploring in detail the pole structure of the electro-nuclear response functions. Making extensive use of the method of dispersion integrals we calculate the full polarization propagator not only for real energies in the spacelike and timelike regime but also in the whole complex energy plane. The latter proved to be necessary in order to identify unphysical causality violating poles which are the consequence of a neglection of vacuum polarization. On the contrary it is shown that Dirac sea effects stabilize the nuclear matter system shifting the unphysical pole from the upper energy plane back to the real axis. The exchange of strength between these real timelike collective excitations and the spacelike energy regime is shown to lead to a reduction of the quasielastic peak as it is seen in electron scattering experiments. Neglecting vacuum polarization one also obtains a reduction of the quasielastic peak but in this case the strength is partly shifted to the causality violating pole mentioned above which consequently cannot be considered as a physical reliable result. Our investigation of the response function in the energy region above the threshold of nucleon anti-nucleon production leads to another remarkable result. Treating the nucleons as point-like Dirac particles we show that for any isospin independent NN-interaction RPA-correlations provide a reduction of the production amplitude for $p\bar p$-pairs by a factor 2.Comment: 19 pages Latex including 12 postscript figure

Asian, Native Hawaiian, and Pacific Islander Populations in the US—Moving From Invisibility to Health Equity

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Zooming in to Advance Health Equity for Heart Failure—Disaggregating Race, Ethnicity, and Social Data

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Addressing Bias and Racism Against Asian American, Native Hawaiian, and Pacific Islander Individuals: A Call to Action to Advance Health Equity and Leadership

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Reforms to Support the Health Care Industry to Address Adverse Health–Related Social Factors

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A Close Binary Star Resolved from Occultation by 87 Sylvia

The star BD+29 1748 was resolved to be a close binary from its occultation by the asteroid 87 Sylvia on 2006 December 18 UT. Four telescopes were used to observe this event at two sites separated by some 80 km apart. Two flux drops were observed at one site, whereas only one flux drop was detected at the other. From the long-term variation of Sylvia, we inferred the probable shape of the shadow during the occultation, and this in turn constrains the binary parameters: the two components of BD+29 1748 have a projected separation of 0.097" to 0.110" on the sky with a position angle 104 deg to 107 deg. The asteroid was clearly resolved with a size scale ranging from 130 to 290 km, as projected onto the occultation direction. No occultation was detected for either of the two known moonlets of 87 Sylvia.Comment: 12 pages, 4 figures, 2 tables; submitted to the PAS

Early winners and losers in dialysis center pay-for-performance

Abstract Background We examined the association of dialysis facility characteristics with payment reductions and change in clinical performance measures during the first year of the United States Centers for Medicare & Medicaid Services (CMS) End Stage Renal Disease Quality Incentive Plan (ESRD QIP) to determine its potential impact on quality and disparities in dialysis care. Methods We linked the 2012 ESRD QIP Facility Performance File to the 2007–2011 American Community Survey by zip code and dichotomized the QIP total performance scores—derived from percent of patients with urea reduction rate > 65, hemoglobin  12 g/dL—as ‘any’ versus ‘no’ payment reduction. We characterized associations between payment reduction and dialysis facility characteristics and neighborhood demographics, and examined changes in facility outcomes between 2007 and 2010. Results In multivariable analysis, facilities with any payment reduction were more likely to have longer operation (OR 1.03 per year), a medium or large number of stations (OR 1.31 and OR 1.42, respectively), and a larger proportion of African Americans (OR 1.25, highest versus lowest quartile), all p < 0.05. Most improvement in clinical performance was due to reduced overtreatment of anemia, a decline in the percentage of patients with hemoglobin ≥ 12 g/dL; for-profits and facilities in African American neighborhoods had the greatest reduction. Conclusions In the first year of CMS pay-for-performance, most clinical improvement was due to reduced overtreatment of anemia. Facilities in African American neighborhoods were more likely to receive a payment reduction, despite their large decline in anemia overtreatment.https://deepblue.lib.umich.edu/bitstream/2027.42/139722/1/12913_2017_Article_2764.pd