Finding Your Literature Match -- A Recommender System

The universe of potentially interesting, searchable literature is expanding continuously. Besides the normal expansion, there is an additional influx of literature because of interdisciplinary boundaries becoming more and more diffuse. Hence, the need for accurate, efficient and intelligent search tools is bigger than ever. Even with a sophisticated search engine, looking for information can still result in overwhelming results. An overload of information has the intrinsic danger of scaring visitors away, and any organization, for-profit or not-for-profit, in the business of providing scholarly information wants to capture and keep the attention of its target audience. Publishers and search engine engineers alike will benefit from a service that is able to provide visitors with recommendations that closely meet their interests. Providing visitors with special deals, new options and highlights may be interesting to a certain degree, but what makes more sense (especially from a commercial point of view) than to let visitors do most of the work by the mere action of making choices? Hiring psychics is not an option, so a technological solution is needed to recommend items that a visitor is likely to be looking for. In this presentation we will introduce such a solution and argue that it is practically feasible to incorporate this approach into a useful addition to any information retrieval system with enough usage.Comment: Contribution to the proceedings of the colloquium Future Professional Communication in Astronomy II, 13-14 April 2010, Cambridge, Massachusetts. 11 pages, 4 figures

E-prints and Journal Articles in Astronomy: a Productive Co-existence

Are the e-prints (electronic preprints) from the arXiv repository being used instead of the journal articles? In this paper we show that the e-prints have not undermined the usage of journal papers in the astrophysics community. As soon as the journal article is published, the astronomical community prefers to read the journal article and the use of e-prints through the NASA Astrophysics Data System drops to zero. This suggests that the majority of astronomers have access to institutional subscriptions and that they choose to read the journal article when given the choice. Within the NASA Astrophysics Data System they are given this choice, because the e-print and the journal article are treated equally, since both are just one click away. In other words, the e-prints have not undermined journal use in the astrophysics community and thus currently do not pose a financial threat to the publishers. We present readership data for the arXiv category "astro-ph" and the 4 core journals in astronomy (Astrophysical Journal, Astronomical Journal, Monthly Notices of the Royal Astronomical Society and Astronomy & Astrophysics). Furthermore, we show that the half-life (the point where the use of an article drops to half the use of a newly published article) for an e-print is shorter than for a journal paper. The ADS is funded by NASA Grant NNG06GG68G. arXiv receives funding from NSF award #0404553Comment: 8 pages, 4 figures, submitted to Learned Publishin

Spin-polarized electron beam generation in the colliding-pulse injection scheme

Employing colliding-pulse injection has been shown to enable high-quality electron beams to be generated from laser-plasma accelerators. Here by leveraging test particle simulations, Hamiltonian analysis, and multidimensional particle-in-cell (PIC) simulations, we lay the theoretical framework of spin-polarized electron beam generation in the colliding-pulse injection scheme. Furthermore, we show that this scheme enables the production of quasi-monoenergetic electron beams in excess of 80\% polarization and tens pC charge with commercial 10-TW-class laser systems.Comment: 11 pages, 10 figure

Dynamic Spanning Trees for connectivity queries on fully-dynamic undirected graphs

Answering connectivity queries is fundamental to fully dynamic graphs where edges and vertices are inserted and deleted frequently. Existing work proposes data structures and algorithms with worst case guarantees. We propose a new data structure, the dynamic tree (D-tree), together with algorithms to construct and maintain it. The D-tree is the first data structure that scales to fully dynamic graphs with millions of vertices and edges and, on average, answers connectivity queries much faster than data structures with worst case guarantees