A table-top laser-based source of short, collimated, ultra-relativistic positron beams

An ultra-relativistic electron beam passing through a thick, high-Z solid target triggers an electromagnetic cascade, whereby a large number of high energy photons and electron-positron pairs are produced. By exploiting this physical process, we present here the first experimental evidence of the generation of ultra-short, highly collimated and ultra-relativistic positron beams following the interaction of a laser-wake field accelerated electron beam with high-Z solid targets. Clear evidence has also been obtained of the generation of GeV electron-positron jets with variable composition depending on the solid target material and thickness. The percentage of positrons in the overall leptonic beam has been observed to vary from a few per cent up to almost fifty per cent, implying a quasi-neutral electron-positron beam. We anticipate that these beams will be of direct relevance to the laboratory study of astrophysical leptonic jets and their interaction with the interstellar medium.

Top incomes under finance-driven capitalism, 1990-2010: power resources and regulatory orders

This article examines the impact of financialisation on the income shares of the top 1% from 1990-2010, through a panel analysis of 14 OECD countries. Drawing together literatures stressing the dependence of income inequality on the structural bargaining power of capital relative to labour, and of the dependence of accumulation on underlying institutionalised modes of state regulation, it shows that financialisation has significantly enhanced top income shares net of underlying controls. Whilst the income shares of the top 1% appear responsive to variables typical of wider studies of personal income inequality, we emphasise distinctive mechanisms of top income growth linked to the rising dominance of financial instruments and actors, facilitated by a historically specific regulatory order. These conditions were key to the emergence of a state of ‘asymmetric bargaining’ which disproportionately enhanced the fortunes of the wealthy. Results thus emphasise the importance of class-biased power resources and underlying regulatory structures, as determinants both of income concentration and of the distribution of economic rewards beyond growth capacity alone.

Temporal Spatial-Keyword Top-k publish/subscribe

Massive amount of data that are geo-tagged and associated with text information are being generated at an unprecedented scale. These geo-textual data cover a wide range of topics. Users are interested in receiving up-to-date tweets such that their locations are close to a user specified location and their texts are interesting to users. For example, a user may want to be updated with tweets near her home on the topic “food poisoning vomiting.” We consider the Temporal Spatial-Keyword Top-k Subscription (TaSK) query. Given a TaSK query, we continuously maintain up-to-date top-k most relevant results over a stream of geo-textual objects (e.g., geo-tagged Tweets) for the query. The TaSK query takes into account text relevance, spatial proximity, and recency of geo-textual objects in evaluating its relevance with a geo-textual object. We propose a novel solution to efficiently process a large number of TaSK queries over a stream of geotextual objects. We evaluate the efficiency of our approach on two real-world datasets and the experimental results show that our solution is able to achieve a reduction of the processing time by 70-80% compared with two baselines.

Anatomising Irish Rebellion: the Cromwellian Delinquency Commissions, the Books of Discrimination and the 1641 Depositions

The recent digitisation of the 1641 depositions has opened up that large and controversial collection of manuscripts to renewed study. The significance of a substantial section of that archive generated in 1653-4 by the work of the Cromwellian delinquency commissions has hitherto been poorly understood. This article sheds new light on the workings of the commissions and on the ways in which the 'delinquency depositions' that they collected helped to shape the implementation of the Cromwellian and Restoration land settlements in Ireland. It also compares the Irish delinquency proceedings to the approach adopted by the Long Parliament in its dealings with royalists in England in the 1640s. In analysing the actual content of the depositions, the article focuses particular attention on County Wexford. The surviving delinquency depositions enable in-depth exploration of many facets of the 1641 rebellion and its aftermath in that region.