899 research outputs found

    Decay-assisted collinear resonance ionization spectroscopy: Application to neutron-deficient francium

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    This paper reports on the hyperfine-structure and radioactive-decay studies of the neutron-deficient francium isotopes 202−206^{202-206}Fr performed with the Collinear Resonance Ionization Spectroscopy (CRIS) experiment at the ISOLDE facility, CERN. The high resolution innate to collinear laser spectroscopy is combined with the high efficiency of ion detection to provide a highly-sensitive technique to probe the hyperfine structure of exotic isotopes. The technique of decay-assisted laser spectroscopy is presented, whereby the isomeric ion beam is deflected to a decay spectroscopy station for alpha-decay tagging of the hyperfine components. Here, we present the first hyperfine-structure measurements of the neutron-deficient francium isotopes 202−206^{202-206}Fr, in addition to the identification of the low-lying states of 202,204^{202,204}Fr performed at the CRIS experiment.Comment: Accepted for publication with Physical Review

    Laser spectroscopy of francium isotopes at the borders of the region of reflection asymmetry

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    The magnetic dipole moments and changes in mean-square charge radii of the neutron-rich 218m,219,229,231Fr^{218m,219,229,231}\text{Fr} isotopes were measured with the newly-installed Collinear Resonance Ionization Spectroscopy (CRIS) beam line at ISOLDE, CERN, probing the 7s 2S1/27s~^{2}S_{1/2} to 8p 2P3/28p~^{2}P_{3/2} atomic transition. The ή⟹r2⟩A,221\delta\langle r^{2}\rangle^{A,221} values for 218m,219Fr^{218m,219}\text{Fr} and 229,231Fr^{229,231}\text{Fr} follow the observed increasing slope of the charge radii beyond N = 126N~=~126. The charge radii odd-even staggering in this neutron-rich region is discussed, showing that 220Fr^{220}\text{Fr} has a weakly inverted odd-even staggering while 228Fr^{228}\text{Fr} has normal staggering. This suggests that both isotopes reside at the borders of a region of inverted staggering, which has been associated with reflection-asymmetric shapes. The g(219Fr)=+0.69(1)g(^{219}\text{Fr}) = +0.69(1) value supports a π1h9/2\pi 1h_{9/2} shell model configuration for the ground state. The g(229,231Fr)g(^{229,231}\text{Fr}) values support the tentative Iπ(229,231Fr)=(1/2+)I^{\pi}(^{229,231}\text{Fr}) = (1/2^{+}) spin, and point to a πs1/2−1\pi s_{1/2}^{-1} intruder ground state configuration.Comment: Accepted for publication with Physical Review

    Models of Individual Blue Stragglers

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    This chapter describes the current state of models of individual blue stragglers. Stellar collisions, binary mergers (or coalescence), and partial or ongoing mass transfer have all been studied in some detail. The products of stellar collisions retain memory of their parent stars and are not fully mixed. Very high initial rotation rates must be reduced by an unknown process to allow the stars to collapse to the main sequence. The more massive collision products have shorter lifetimes than normal stars of the same mass, while products between low mass stars are long-lived and look very much like normal stars of their mass. Mass transfer can result in a merger, or can produce another binary system with a blue straggler and the remnant of the original primary. The products of binary mass transfer cover a larger portion of the colour-magnitude diagram than collision products for two reasons: there are more possible configurations which produce blue stragglers, and there are differing contributions to the blended light of the system. The effects of rotation may be substantial in both collision and merger products, and could result in significant mixing unless angular momentum is lost shortly after the formation event. Surface abundances may provide ways to distinguish between the formation mechanisms, but care must be taking to model the various mixing mechanisms properly before drawing strong conclusions. Avenues for future work are outlined.Comment: Chapter 12, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G. Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe

    Mobilising Knowledge through Global Partnerships to Support Research-informed Teaching: Five Models for Translational Research

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    Education Futures Collaboration Charity The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Improving the quality of teaching is of global concern: UNESCO’s Sustainable Development Goal (SDG) 4c in the Education 2030: Framework for Action calls for high quality teaching for all. The OECD challenges the education system to improve Knowledge Management. JET’s (2015) special issue: Translational Research (TR) and Knowledge Mobilisation in Teacher Education introduced the concept of ‘translational’ or ‘theory to practice’ research - well-established in medicine but not in education. Five TR models were subsequently developed by the MESH charity’s international network with organisations in South Africa, Bangladesh, Australia, Pakistan, UK. These distinct models engage 1) university staff and teachers 2) subject associations, 3) research units, 4) an international NGO working in crisis settings, 5) PhD tutors and students. Each model shares common features forming the MESH Translational Research methodology introduced in this article. A TR repository is part of the MESH knowledge mobilisation strategy giving teachers access to research summaries which, overtime, accumulate knowledge. TR publications called MESHGuides (www.meshguides.org) complement existing forms of publication. This article proposes the MESH TR methodology as one affordable and scalable solution to OECD and UNESCO’s challenges of keeping teachers up-to-date and making new knowledge accessible to teachers regardless of location

    Analysing How People Orient to and Spread Rumours in Social Media by Looking at Conversational Threads

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    As breaking news unfolds people increasingly rely on social media to stay abreast of the latest updates. The use of social media in such situations comes with the caveat that new information being released piecemeal may encourage rumours, many of which remain unverified long after their point of release. Little is known, however, about the dynamics of the life cycle of a social media rumour. In this paper we present a methodology that has enabled us to collect, identify and annotate a dataset of 330 rumour threads (4,842 tweets) associated with 9 newsworthy events. We analyse this dataset to understand how users spread, support, or deny rumours that are later proven true or false, by distinguishing two levels of status in a rumour life cycle i.e., before and after its veracity status is resolved. The identification of rumours associated with each event, as well as the tweet that resolved each rumour as true or false, was performed by journalist members of the research team who tracked the events in real time. Our study shows that rumours that are ultimately proven true tend to be resolved faster than those that turn out to be false. Whilst one can readily see users denying rumours once they have been debunked, users appear to be less capable of distinguishing true from false rumours when their veracity remains in question. In fact, we show that the prevalent tendency for users is to support every unverified rumour. We also analyse the role of different types of users, finding that highly reputable users such as news organisations endeavour to post well-grounded statements, which appear to be certain and accompanied by evidence. Nevertheless, these often prove to be unverified pieces of information that give rise to false rumours. Our study reinforces the need for developing robust machine learning techniques that can provide assistance in real time for assessing the veracity of rumours. The findings of our study provide useful insights for achieving this aim

    Identification of isomeric states in the N=73 neutron-deficient nuclei 132Pr and 130La

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    Decays from isomeric states in the neutron-deficient N=73 nuclei 132Pr and 130La have been observed for the first time. Half-lives of 486(70) ns and 2.46(4) ÎŒs were measured for two isomeric states in 132Pr. The decay from the 486 ns (8‑) isomer has been interpreted as a hindered E1 transition from the bandhead state of the excited πh11/2⊗Μg7/2 configuration. The decay from the 2.5 ÎŒs (8+) isomer is consistent with the Weisskopf estimate for a low-energy E2 transition. An analogous 0.74(3) ÎŒs decay from an (8+) isomer in the neighboring isotone 130La has also been observed which similarly can be explained if the transition has E2 character. The Weisskopf interpretation for the isomer hindrance is strengthened by the lack of evidence for shape or K isomerism due to the Îł-soft shapes predicted by configuration-constrained potential-energy-surface calculations

    MACSIMS : multiple alignment of complete sequences information management system

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    BACKGROUND: In the post-genomic era, systems-level studies are being performed that seek to explain complex biological systems by integrating diverse resources from fields such as genomics, proteomics or transcriptomics. New information management systems are now needed for the collection, validation and analysis of the vast amount of heterogeneous data available. Multiple alignments of complete sequences provide an ideal environment for the integration of this information in the context of the protein family. RESULTS: MACSIMS is a multiple alignment-based information management program that combines the advantages of both knowledge-based and ab initio sequence analysis methods. Structural and functional information is retrieved automatically from the public databases. In the multiple alignment, homologous regions are identified and the retrieved data is evaluated and propagated from known to unknown sequences with these reliable regions. In a large-scale evaluation, the specificity of the propagated sequence features is estimated to be >99%, i.e. very few false positive predictions are made. MACSIMS is then used to characterise mutations in a test set of 100 proteins that are known to be involved in human genetic diseases. The number of sequence features associated with these proteins was increased by 60%, compared to the features available in the public databases. An XML format output file allows automatic parsing of the MACSIM results, while a graphical display using the JalView program allows manual analysis. CONCLUSION: MACSIMS is a new information management system that incorporates detailed analyses of protein families at the structural, functional and evolutionary levels. MACSIMS thus provides a unique environment that facilitates knowledge extraction and the presentation of the most pertinent information to the biologist. A web server and the source code are available at
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