Twenty-first century ownership: individual and community stakes

Community development

Persistent Memory Programming Abstractions in Context of Concurrent Applications

The advent of non-volatile memory (NVM) technologies like PCM, STT, memristors and Fe-RAM is believed to enhance the system performance by getting rid of the traditional memory hierarchy by reducing the gap between memory and storage. This memory technology is considered to have the performance like that of DRAM and persistence like that of disks. Thus, it would also provide significant performance benefits for big data applications by allowing in-memory processing of large data with the lowest latency to persistence. Leveraging the performance benefits of this memory-centric computing technology through traditional memory programming is not trivial and the challenges aggravate for parallel/concurrent applications. To this end, several programming abstractions have been proposed like NVthreads, Mnemosyne and intel's NVML. However, deciding upon a programming abstraction which is easier to program and at the same time ensures the consistency and balances various software and architectural trade-offs is openly debatable and active area of research for NVM community. We study the NVthreads, Mnemosyne and NVML libraries by building a concurrent and persistent set and open addressed hash-table data structure application. In this process, we explore and report various tradeoffs and hidden costs involved in building concurrent applications for persistence in terms of achieving efficiency, consistency and ease of programming with these NVM programming abstractions. Eventually, we evaluate the performance of the set and hash-table data structure applications. We observe that NVML is easiest to program with but is least efficient and Mnemosyne is most performance friendly but involves significant programming efforts to build concurrent and persistent applications.Comment: Accepted in HiPC SRS 201

A formalism for the construction of binary neutron stars with arbitrary circulation

Most numerical models of binary stars - in particular neutron stars in compact binaries - assume the companions to be either corotational or irrotational. Either one of these assumptions leads to a significant simplification in the hydrodynamic equations of stationary equilibrium. In this paper we develop a new formalism for the construction of binary stars with circulation intermediate between corotational and irrotational. Generalizing the equations for irrotational flow we cast the Euler equation, which is an algebraic equation in the case of corotational or irrotational fluid flow, as an elliptic equation for a new auxiliary quantity. We also suggest a parameterized decomposition of the fluid flow that allows for a variation of the stellar circulation.Comment: 8 pages, no figures; published version with erratu

From Bad to Worse: Senior Economic Insecurity on the Rise

Based on the Senior Financial Stability Index, examines the increase in the number of economically insecure seniors by race/ethnicity, gender, and marital status between 2004 and 2008; contributing factors; and options for reversing the trend

Luminosity versus Rotation in a Supermassive Star

We determine the effect of rotation on the luminosity of supermassive stars. We apply the Roche model to calculate analytically the emitted radiation from a uniformly rotating, radiation-dominated supermassive configuration. We find that the luminosity at maximum rotation, when mass at the equator orbits at the Kepler period, is reduced by ~36% below the usual Eddington luminosity from the corresponding nonrotating star. A supermassive star is believed to evolve in a quasistationary manner along such a maximally rotating ``mass-shedding'' sequence before reaching the point of dynamical instability; hence this reduced luminosity determines the evolutionary timescale. Our result therefore implies that the lifetime of a supermassive star prior to dynamical collapse is ~56% longer than the value typically estimated by employing the usual Eddington luminosity.Comment: 5 pages, 2 figures, uses emulateapj.sty; to appear in Ap

By a Thread: The New Experience of America's Middle Class

Developed in collaboration with the Institute on Assets and Social Policy at Brandeis University, By a Thread: The New Experience of America's Middle Class looks at the financial security of the middle class using the innovative Middle Class Security Index, rating household stability across five core economic factors: assets, educational achievement, housing costs, budget and healthcare. The Index provides a comprehensive portrait of how well middle-class families are faring in each of these areas, with spotlight on the strengths and vulnerabilities of today's middle class

Hard Choices: Navigating the Economic Shock of Unemployment

During the Great Recession of 2007 to 2009, millions of Americans faced severe economic hardship, forcing difficult decisions about how to stabilize their families' financial well-being and prevent downward economic mobility. Americans with savings were forced to weigh immediate needs against long-term investments, choosing whether to deplete personal assets in order to stay afloat. Those without wealth to fall back on were in an even more precarious position, leading them to turn to family assistance, debt, and other public and private supports when available.This study examines how families weather economic shocks through a close focus on one particular event -- the experience of unemployment, with specific attention to differences by race and family income. The analysis used a nationally representative sample of working-age families from the Panel Study of Income Dynamics or PSID, following the same households from 1999 to 2009. To provide greater insight into the challenges and choices families faced, the report also drew on a unique longitudinal data set of in-depth interviews with 51 families that endured one month or more of unemployment between 1998 and 2012