Black-hole jets without large-scale net magnetic flux

We propose a scenario for launching relativistic jets from rotating black holes, in which small-scale magnetic flux loops, sustained by disc turbulence, are forced to inflate and open by differential rotation between the black hole and the accretion flow. This mechanism does not require a large-scale net magnetic flux in the accreting plasma. Estimates suggest that the process could operate effectively in many systems, and particularly naturally and efficiently when the accretion flow is retrograde. We present the results of general-relativistic force-free electrodynamic simulations demonstrating the time evolution of the black hole's magnetosphere, the cyclic formation of jets, and the effect of magnetic reconnection. The jets are highly variable on timescales ~ 10-10^3 r_ g/c, where r_g is the black hole's gravitational radius. The reconnecting current sheets observed in the simulations may be responsible for the hard X-ray emission from accreting black holes.Comment: 5 pages, 2 figures. Accepted for publication in MNRAS Letter

The Reality of Measuring Human Service Programs: Results of a Survey

In the summer of 2013, Idealware created and distributed a survey to learn how human service organizations from their own mailing list are actually using technology to measure and evaluate the outcomes of their programs. The suvey looked at a general overview of outcomes measurement and program evaluation topics, from how frequently they look at data and how much time they spend doing so to what types of metrics the organizations were tracking. To further understand the realities of measuring program effectiveness, Idealware conducted a site visit and interview of three human service organizations in Portland, Maine. The results clearly show that the respondents are struggling to measure their programs

Web-based multi-party computation with application to anonymous aggregate compensation analytics

We describe the definition, design, implementation, and deployment of a multi-party computation protocol and supporting web-based infrastructure. The protocol and infrastructure constitute a software application that allows groups of cooperating parties, such as companies or other organizations, to collect aggregate data for statistical analysis without revealing the data of individual participants. The application was developed specifically to support a Boston Women's Workforce Council (BWWC) study of the gender wage gap among employers within the Greater Boston Area. The application was deployed successfully to collect aggregate statistical data pertaining to compensation levels across genders and demographics at a number of participating organizations.We would like to acknowledge all the members of the Boston Women's Workforce Council (BWWC), and to thank in particular Christina M. Knowles and Katie A. Johnston, who led the effort to organize participants and deploy the protocol as part of the 100% Talent: The Boston Women's Compact effort [1, 2]. We would also like to acknowledge the Boston University Initiative on Cities, and in particular Executive Director Katherine Lusk, who brought this potential application of secure multi-party computation to our attention. Both the BWWC and the Initiative on Cities contributed funding to complete this work. We would also like to acknowledge the Hariri Institute at Boston University for contributing research and software development resources. Support was also provided in part by Smart-city Cloud-based Open Platform and Ecosystem (SCOPE), an NSF Division of Industrial Innovation and Partnerships PFI:BIC project under award #1430145, and by Modular Approach to Cloud Security (MACS), an NSF CISE CNS SaTC Frontier project under award #1414119

A Consumers Guide to Software for Volunteer Management

Volunteer-based organizations have to keep track of a lot of data—for example, contact info, schedules, time sheets and job sites—and the right software can help, freeing time for managing volunteers. There are a number of products out there, but it's surprisingly hard to find information about them.We hope this report remedies that. We designed it to serve as an introduction to volunteer management software: what's out there, what to expect and how the different solutions compare

A Consumers Guide to Grants Management Systems 2016

This report has been released by Grants Managers Network (GMN) and Technology Affinity Group (TAG), with research conducted by Idealware. The report compares 29 grants management systems across 174 requirements criteria, looks at what each system does, and compares the strengths and weaknesses of each system available to grantmakers. The report looks at how they stack up against high-level categories and details the functionality of each system against specific criteria important to the grant-making community

‘Flash Crash’: The first market crash in the era of algorithms and automated trading

How non-designated intraday intermediaries responded in the E-mini S&P 500 futures market crash on 6 May 2010 - by Andrei Kirilenko, Albert Kyle, Mehrdad Samadi, and Tugkan Tuzu

The flash crash: The impact of high frequency trading on an electronic market

The Flash Crash, a brief period of extreme market volatility on May 6, 2010, raised questions about the current structure of the U.S. financial markets. We use audit-trail data to describe the structure of the E-mini S&P 500 stock index futures market on May 6. We ask three questions. How did High Frequency Traders (HFTs) trade on May 6? What may have triggered the Flash Crash? What role did HFTs play in the Flash Crash? We conclude that HFTs did not trigger the Flash Crash, but their responses to the unusually large selling pressure on that day exacerbated market volatility

Application of the dual-kinetic-balance sets in the relativistic many-body problem of atomic structure

The dual-kinetic-balance (DKB) finite basis set method for solving the Dirac equation for hydrogen-like ions [V. M. Shabaev et al., Phys. Rev. Lett. 93, 130405 (2004)] is extended to problems with a non-local spherically-symmetric Dirac-Hartree-Fock potential. We implement the DKB method using B-spline basis sets and compare its performance with the widely-employed approach of Notre Dame (ND) group [W.R. Johnson and J. Sapirstein, Phys. Rev. Lett. 57, 1126 (1986)]. We compare the performance of the ND and DKB methods by computing various properties of Cs atom: energies, hyperfine integrals, the parity-non-conserving amplitude of the $6s_{1/2}-7s_{1/2}$ transition, and the second-order many-body correction to the removal energy of the valence electrons. We find that for a comparable size of the basis set the accuracy of both methods is similar for matrix elements accumulated far from the nuclear region. However, for atomic properties determined by small distances, the DKB method outperforms the ND approach. In addition, we present a strategy for optimizing the size of the basis sets by choosing progressively smaller number of basis functions for increasingly higher partial waves. This strategy exploits suppression of contributions of high partial waves to typical many-body correlation corrections.Comment: 10 page