Private Pareto Optimal Exchange

We consider the problem of implementing an individually rational, asymptotically Pareto optimal allocation in a barter-exchange economy where agents are endowed with goods and have preferences over the goods of others, but may not use money as a medium of exchange. Because one of the most important instantiations of such economies is kidney exchange -- where the "input"to the problem consists of sensitive patient medical records -- we ask to what extent such exchanges can be carried out while providing formal privacy guarantees to the participants. We show that individually rational allocations cannot achieve any non-trivial approximation to Pareto optimality if carried out under the constraint of differential privacy -- or even the relaxation of \emph{joint} differential privacy, under which it is known that asymptotically optimal allocations can be computed in two-sided markets, where there is a distinction between buyers and sellers and we are concerned only with privacy of the buyers~\citep{Matching}. We therefore consider a further relaxation that we call \emph{marginal} differential privacy -- which promises, informally, that the privacy of every agent $i$ is protected from every other agent $j \neq i$ so long as $j$ does not collude or share allocation information with other agents. We show that, under marginal differential privacy, it is possible to compute an individually rational and asymptotically Pareto optimal allocation in such exchange economies

Free wake analysis of helicopter rotor flow fields using a coupled voricity embedding/fractional step method

A hybrid CFD (Computational Fluid Dynamics) method combining a potential-based Vorticity Embedding method with an Euler solver is presented and validated for isolated rotor flows First, a formulation of Vorticity Embedding is developed and validated for Cartesian grids This formulation is utilized together with simple lifting lines to represent an isolated rotor in hover The results for an isolated rotor are then compared with experiment The method is then hybridized by coupling the Vorticity Embedding grid containing the rotor to a region containing a ground plane where a standard finite difference Euler solver is utilized Initial results from this hybrid scheme are presented including a demonstration of the code\u27s potential to calculate the ground vortex roll-up generated by a rotor in ground effect in the presence of a cross-win

Developing Reciprocal Community in Jackson Baptist Church

Jackson Baptist Church lacks reciprocal community amongst its regular attendees and visitors. The focus is on the large group gathering on Sundays which has developed a consumer-based culture within the church. In both the Old and New Testaments, there are examples of reciprocal community. Acts 2:44(NASB) it states, “And all those who had believed were together and had all things in common.” The church in the first century developed an active reciprocal community. Strategies laid out in scripture and church history can assist building community. This project by taking those strategies will conduct an awareness campaign at Jackson Baptist on reciprocal community. This will be done through a pre-test of fifty questions to be taken prior to a class on community. Following the class, the same survey will be filled out again to gauge if the class had a direct effect on the responses from the participants. The data collected will be analyzed using the Paired-T Test. Using the Paired-T Test an average mean will be discovered to show if the course had a direct effect on the responses and it was not by chance. Following the results, the purpose of the research is to begin developing reciprocal community within Jackson Baptist Church

Tidal Disruption Event Host Galaxies in the Context of the Local Galaxy Population

We study the properties of tidal disruption event (TDE) host galaxies in the context of a catalog of ~500,000 galaxies from the Sloan Digital Sky Survey. We explore whether selection effects can account for the overrepresentation of TDEs in E+A/post-starburst galaxies by creating matched galaxy samples. Accounting for possible selection effects due to black hole (BH) mass, redshift completeness, strong AGN presence, bulge colors, and surface brightness can reduce the apparent overrepresentation of TDEs in E+A host galaxies by a factor of ~4 (from ~$\times$100-190 to ~$\times$25-48), but cannot fully explain the preference. We find that TDE host galaxies have atypical photometric properties compared to similar, "typical" galaxies. In particular, TDE host galaxies tend to live in or near the "green valley" between star-forming and passive galaxies, and have bluer bulge colors ($\Delta (g-r) \approx 0.3$ mag), lower half-light surface brightnesses (by ~1 mag/arcsec$^2$), higher Sersic indices ($\Delta n_{\rm g} \approx 3$), and higher bulge-to-total-light ratios ($\Delta B/T \approx 0.5$) than galaxies with matched BH masses. We find that TDE host galaxies appear more centrally concentrated and that all have high galaxy Sersic indices and $B/T$ fractions---on average in the top 10% of galaxies of the same BH mass---suggesting a higher nuclear stellar density. We identify a region in Sersic index and BH mass parameter space that contains ~2% of our reference catalog galaxies but $\ge\!60\%$ of TDE host galaxies. The unique photometric properties of TDE host galaxies may be useful for selecting candidate TDEs for spectroscopic follow-up observations in large transient surveys.Comment: 26 pages, 11 figures, 5 tables. Published in Ap

Why did Democrats lose seats in the 2020 elections? More incumbents ran in more competitive districts.

Despite expectations that they would ride Joe Biden’s successful presidential election coattails to an increased majority in the US House of Representatives, the Democrats are likely to find themselves with a reduced majority heading into the 117th Congress. Ryan Williamson and Jamie Carson write that moderates likely lost their seats in this election because they were defending very competitive and often Republican-leaning districts in a nationalized election. With this in mind, they comment that Democrats must now consider how to promote their often diverse messages in ways that satisfies both the progressive and more moderate parts of the party

How High-Need Patients Experience the Health Care System in Nine Countries

U.S. health care costs are disproportionately concentrated among older adults with multiple chronic conditions or functional limitations—a population often referred to as "high-need" patients. This analysis uses data from the Commonwealth Fund 2014 International Health Policy Survey of Older Adults to investigate health care use, quality, and experiences among high-need patients in nine countries compared with other older adults. High-need patients use a greater amount of health care services and also experience more coordination problems and financial barriers to care compared with other older adults. Disparities are particularly pronounced in the United States. The comparative success of other countries, particularly in reducing financial barriers to care, may be a product of policies that specifically target high-need patients. Similarly focusing on these populations in the U.S. and effectively managing their care may improve their health status while reducing overall costs