Stellar binaries in galactic nuclei: tidally stimulated mergers followed by tidal disruptions

We investigate interactions of stellar binaries in galactic nuclear clusters with a massive black hole (MBH). We consider binaries on highly eccentric orbits around the MBH that change due to random gravitational interactions with other stars in the nuclear stellar cluster. The pericenters of the orbits perform a random walk, and we consider cases where this random walk slowly brings the binary to the Hills tidal separation radius (the so-called empty loss-cone regime). However, we find that in a majority of cases the expected separation does not occur and instead the members of the binary merge together. This happens because the binary's eccentricity is excited by tidal interactions with the MBH, and the relative excursions of the internal eccentricity of the binary far exceed those in its internal semimajor axis. This frequently reduces the pericenter separation to values below typical stellar diameters, which induces a significant fraction of such binaries to merge ($\gtrsim 75\%$ in our set of numerical experiments). Stellar tides do not appreciably change the total rate of mergers but circularise binaries, leading to a significant fraction of low-eccentricity, low-impact-velocity mergers. Some of the stellar merger products will then be tidally disrupted by the MBH within $\sim 10^6$ years. If the merger strongly enhances the magnetic field of the merger product, this process could explain observations of prompt relativistic jet formation in some tidal disruption events

Building the capacity to use research in education requires a sustained strategic and systemic effort

The English education context offers positive elements and challenges for evidence-informed policy and practice. The issues are well understood but Carol Campbell and Ben Levin argue there is a lack of a strategic approach to improving knowledge mobilisation in the sector. Renewed attention is needed to build such capacities if schools are to benefit from the findings of high quality research

Research Use by Leaders in Canadian School Districts

This paper, part of a larger study, investigates the ways research is used by leaders in Canadian schools and districts, an area in which there is relatively little empirical evidence. The paper analyzes survey results from 188 education leaders in 11 school districts across Canada about school and district practices related to the use of research. Results indicate a growing awareness in districts of the importance of research use, reported district capacity, and many kinds of support available for research-related activities; however, actual research use remains modest. Districts appear to have relatively weak processes and systems for finding, sharing and using relevant research

Assessing Organizational Efforts to Mobilize Research Knowledge in Education

This paper presents a framework for evaluating efforts by organizations to share research as exemplified on their websites, then reports the result of an evaluation of these efforts in 100 organizations. The result shows that the overall research sharing efforts of these organizations are modest and not well aligned to evidence on effective practice in this area. Organizations tend to devote more efforts to making products available while interpersonal strategies, though more effective, are less used. Most efforts involve one way communication to potential users. The paper concludes with suggestions for practice and for further research

What Shapes Inner-City Education Policy?

This paper is part of a larger study looking at the issues involved as two large urban Canadian school boards, in Winnipeg and Toronto, responded to the demands of poor, inner city areas over the last thirty years of the twentieth century. In this paper we focus our attention on the broader stage on which education policy takes place. We draw from our data three overarching themes that we believe are critical for understanding change in inner-city education over this period. These are: 1) The diminishing role of school boards, as provincial governments took more control of education policy and limited the scope of school boards, 2) The importance of unique, and sometimes unexpected local events, and 3) The powerful implications for schools and education policy of increasing population diversity in cities.

What Shapes Inner-City Education Policy?

This paper is part of a larger study looking at the issues involved as two large urban Canadian school boards, in Winnipeg and Toronto, responded to the demands of poor, inner city areas over the last thirty years of the twentieth century. In this paper we focus our attention on the broader stage on which education policy takes place. We draw from our data three overarching themes that we believe are critical for understanding change in inner-city education over this period. These are: 1) The diminishing role of school boards, as provincial governments took more control of education policy and limited the scope of school boards, 2) The importance of unique, and sometimes unexpected local events, and 3) The powerful implications for schools and education policy of increasing population diversity in cities

Deciding what to eat

A signaling pathway directs cells to degrade peroxisomes while leaving other organelles untouched

What Does It Take to Scale Up Innovations?

Various education innovations are often proposed as solutions to the problems of education in the United States. Moving an innovation from a few schools to a great many, so it can have a regional or national impact, is very challenging, however. This brief discusses the problem of scaling innovations in education in the United States so that they can serve very large numbers of students. It begins with a general discussion of the issues involved, develops a set of five criteria for assessing challenges of scaling, and then uses three programs widely discussed in the U.S. as examples of the challenges involved: Teach for America (an approach to teacher development), KIPP (a whole-school reform model) and the Harlem Children’s Zone (a school-plus-community model). Five criteria are applied to assess scalability: cost, human capacity, tools and infrastructure, political support, and external or non-school factors. Many innovations appear to have significant additional costs—for example the additional services offered by HCZ or the longer day and year in KIPP. The non-financial challenges, however, such as being able to find enough highly skilled people, can be just as significant and are often underestimated in discussions of scaling. One cannot assume that a popular innovation necessarily represents a potential system-wide solution. Every school system should have a way to assess the potential value and challenge in adopting innovations. The goal should be to avoid either excessive enthusiasm or excessive skepticism, but to maintain a reasoned approach that over time yields collective learning. More independent research on the costs and benefits of major innovations is also required. Recommendations All parties should avoid the temptation to proclaim small-scale innovations as the solutions to large-scale problems in education; rather they should be seen as promising ideas requiring further study before widespread adoption. There should be a more rigorous process for evaluating promising innovations to determine both costs and benefits, involving fair evaluations done by independent and neutral parties. There should be full and open access to data on costs and outcomes of innovations

CAN SIMPLE INTERVENTIONS INCREASE RESEARCH USE IN SECONDARY SCHOOLS?

A variety of interventions have been attempted in education and other fields to increase the use of research use in policy and practice. However, there is still limited research on the impact of these interventions. This paper uses survey and qualitative data to analyze three interventions designed to increase research use among secondary school leaders in nine Canadian school districts. These interventions were found to have little impact, but were more successful where (1) designated facilitators were involved and (2) research used was connected to existing priority issues. The research design for this study (measuring the change in agreement with particular bodies of research knowledge using interventions and pre-post design) is a promising methodology to measure both research use and impact

Secret Sharing Based on a Hard-on-Average Problem

The main goal of this work is to propose the design of secret sharing schemes based on hard-on-average problems. It includes the description of a new multiparty protocol whose main application is key management in networks. Its unconditionally perfect security relies on a discrete mathematics problem classiffied as DistNP-Complete under the average-case analysis, the so-called Distributional Matrix Representability Problem. Thanks to the use of the search version of the mentioned decision problem, the security of the proposed scheme is guaranteed. Although several secret sharing schemes connected with combinatorial structures may be found in the bibliography, the main contribution of this work is the proposal of a new secret sharing scheme based on a hard-on-average problem, which allows to enlarge the set of tools for designing more secure cryptographic applications