A Short Wavelength GigaHertz Clocked Fiber-Optic Quantum Key Distribution System

A quantum key distribution system has been developed, using standard telecommunications optical fiber, which is capable of operating at clock rates of greater than 1 GHz. The quantum key distribution system implements a polarization encoded version of the B92 protocol. The system employs vertical-cavity surface-emitting lasers with emission wavelengths of 850 nm as weak coherent light sources, and silicon single photon avalanche diodes as the single photon detectors. A distributed feedback laser of emission wavelength 1.3 micro-metres, and a linear gain germanium avalanche photodiode was used to optically synchronize individual photons over the standard telecommunications fiber. The quantum key distribution system exhibited a quantum bit error rate of 1.4%, and an estimated net bit rate greater than 100,000 bits-per-second for a 4.2 km transmission range. For a 10 km fiber range a quantum bit error rate of 2.1%, and estimated net bit rate of greater than 7,000 bits-per-second was achieved.Comment: Pre-press versio

Perturbative QCD with Quark and Gluon Condensates

QCD perturbation theory using quark and gluon propagators that have an extra term at zero four-momentum is equivalent to standard PQCD in the presence of massless quark and gluon pairs in the perturbative vacuum. We verify at low orders in perturbation theory that $\neq 0$ and that quarks acquire a constituent mass. Thus chiral symmetry is spontaneously broken, and the conservation of the axial vector current ensures a massless pion. The gluon pairs generate an $$ expectation value and a tachyonic gluon mass. Lorentz and gauge symmetry is preserved, and the short-distance structure of PQCD is unaffected. The modified perturbative expansion thus contains relevant elements of QCD at both short and long distances.Comment: 12 pages, 2 figure

Detecting Important Life Events on Twitter Using Frequent Semantic and Syntactic Subgraphs

Identifying global events from social media has been the focus of much research in recent years. However, the identification of personal life events poses new requirements and challenges that have received relatively little research attention. In this paper we explore a new approach for life event identification, where we expand social media posts into both semantic, and syntactic networks of content. Frequent graph patterns are mined from these networks and used as features to enrich life-event classifiers. Results show that our approach significantly outperforms the best performing baseline in accuracy (by 4.48% points) and F-measure (by 4.54% points) when used to identify five major life events identified from the psychology literature: Getting Married, Having Children, Death of a Parent, Starting School, and Falling in Love. In addition, our results show that, while semantic graphs are effective at discriminating the theme of the post (e.g. the topic of marriage), syntactic graphs help identify whether the post describes a personal event (e.g. someone getting married)

Heathland creation on improved grassland using sulphur: is there a conflict between optimal application rates for plant and animal communities?

We examined the effectiveness of using elemental sulphur (a soil acidifier) as a method for creating heathland on improved pasture. We determined i) optimal rate of sulphur application to control mesotrophic grasses ii) if invertebrates avoid areas of sulphur application. Results indicated that optimal sulphur application attracted invertebrates

Determining citizens’ opinions about stories in the news media: analysing Google, Facebook and Twitter

We describe a method whereby a governmental policy maker can discover citizens’ reaction to news stories. This is particularly relevant in the political world, where governments’ policy statements are reported by the news media and discussed by citizens. The work here addresses two main questions: whereabouts are citizens discussing a news story, and what are they saying? Our strategy to answer the first question is to find news articles pertaining to the policy statements, then perform internet searches for references to the news articles’ headlines and URLs. We have created a software tool that schedules repeating Google searches for the news articles and collects the results in a database, enabling the user to aggregate and analyse them to produce ranked tables of sites that reference the news articles. Using data mining techniques we can analyse data so that resultant ranking reflects an overall aggregate score, taking into account multiple datasets, and this shows the most relevant places on the internet where the story is discussed. To answer the second question, we introduce the WeGov toolbox as a tool for analysing citizens’ comments and behaviour pertaining to news stories. We first use the tool for identifying social network discussions, using different strategies for Facebook and Twitter. We apply different analysis components to analyse the data to distil the essence of the social network users’ comments, to determine influential users and identify important comments

The changing concept of work:When does typical work become atypical

In most countries, a standard (or core) model of employment relationship (i.e. full-time work under an open-ended employment contract) typically receives the greatest labour and social security protection, with divergent work arrangements receiving less protection in correlation to the magnitude of the differences between the former and the latter. However, recent developments concerning non-standard forms of work may question this dynamic. In this article, we examine the nature and current evolution of the standard employment relationship, then analyse how other forms of work deviate from this standard. In order to do so, we draw on the conclusions of the numerous studies recently published by scholars and international organisations in the wake of the growing public debate on the ‘new world of work’. Afterwards, we analyse the situation of non-standard workers under certain social security systems, in order to determine how those systems have approached the divergent character of these forms of work. This leads us to identify the main challenges that social security systems experience when faced with non-standard forms of work. The article concludes by addressing the need to adapt the basic principles of social security to the atypical features of non-standard work