187 research outputs found

    High Energy Neutrinos from the TeV Blazar 1ES 1959+650

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    The AMANDA neutrino telescope has recently reported the detection of high-energy neutrinos spatially and temporally coincident with the flaring of the TeV blazar 1ES 1959+650. At present, the statistical significance of this observation cannot be reliably assessed, however. In this letter, we investigate whether circumstances exist where the source can produce the flux implied by the coincident events. We show that if the TeV gamma-ray emission observed from 1ES 1959+650 or other nearby TeV blazars is the result of accelerated protons interacting with nucleons, it is reasonable that AMANDA could detect several events during a flaring period. Such rates require that the spectral index of the source be rather high (for instance ∌2.8\sim2.8 for 1ES 1959+650) and that the Lorentz factor of the jet be fairly small (Γ∌1\Gamma \sim 1).Comment: 9 pages, 2 figure

    Synoptic studies of seventeen blazars detected in very high-energy gamma-rays

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    Since 2002, the number of detected blazars at gamma-ray energies above 100 GeV has more than doubled. I study 17 blazars currently known to emit E>100 GeV gamma rays. Their intrinsic energy spectra are reconstructed by removing extragalactic background light attenuation effects. Luminosity and spectral slope in the E>100 GeV region are then compared and correlated among each other, with X-ray, optical and radio data, and with the estimated black hole (BH) masses of the respective host galaxies. According to expectations from synchrotron self-Compton emission models, a correlation on the 3.6-sigma significance level between gamma-ray and X-ray fluxes is found, while correlations between gamma-ray and optical/radio fluxes are less pronounced. Further, a general hardening of the E>100 GeV spectra with increasing gamma-ray luminosity is observed. This goes in line with a correlation of the gamma-ray luminosity and the synchrotron peak frequency, which is also seen. Tests for possible selection effects reveal a hardening of the spectra with increasing redshift. The gamma-ray emission might depend on the mass of the central BH. The studied blazars show no correlation of the BH masses with the spectral index and the luminosity in the E>100 GeV region. Also temporal properties of the X-ray and E>100 GeV gamma-ray flux are considered. No general trends are found, except that the blazars with the most massive BHs do not show particularly high duty cycles. In general, VHE flare time-scales are not found to scale with the BH mass. As a specific application of the luminosity study, a constraint for the still undetermined redshift of the blazar PG 1553+113 is discussed.Comment: 17 pages, 18 figures, MNRAS in press. Abstract extended; minor modifications in sect. 3, 5.5; Fig. 7c corrected; references update

    A Search for TeV Gamma-Ray Emission from High-Peaked Flat Spectrum Radio Quasars Using the Whipple Air-Cherenkov Telescope

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    Blazars have traditionally been separated into two broad categories based upon their optical emission characteristics; BL Lacs, with faint or no emission lines, and flat spectrum radio quasars (FSRQs) with prominent, broad emission lines. The spectral energy distribution of FSRQs has generally been thought of as being more akin to the low-peaked BL Lacs, which exhibit a peak in the infrared region of the spectrum, as opposed to high-peaked BL Lacs (HBLs), which exhibit a peak in UV/X-ray region of the spectrum. All blazars currently confirmed as sources of TeV emission are HBLs. Recent surveys have found several FSRQs exhibiting spectral properties similar to HBLs, particularly the synchrotron peak frequency. These objects are potential sources of TeV emission according to several models of blazar jet emission and blazar evolution. Measurements of TeV flux or upper limits could impact existing theories explaining the links between different blazar types and could have a significant impact on our understanding of the nature of objects that are capable of TeV emission. In particular, the presence (or absence) of TeV emission from FSRQs could confirm (or cast doubt upon) recent evolutionary models that expect intermediate objects in a transitionary state between FSRQ and BL Lac. The Whipple 10 meter imaging air-Cherenkov gamma-ray telescope is well suited for TeV gamma-ray observations. Using the Whipple telescope, we have taken data on a small selection of nearby(z<0.1 in most cases), high-peaked FSRQs. Although one of the objects, B2 0321+33, showed marginal evidence of flaring, no significant emission was detected. The implications of this paucity of emission and the derived upper limits are discussed.Comment: accepted for publication in Astrophysical Journa

    The politics of access in fieldwork: Immersion, backstage dramas and deception

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    YesGaining access in fieldwork is crucial to the success of research, and may often be problematic because it involves working in complex social situations. This paper examines the intricacies of access, conceptualizing it as a fluid, temporal and political process that requires sensitivity to social issues and to potential ethical choices faced by both researchers and organization members. Our contribution lies in offering ways in which researchers can reflexively negotiate the challenges of access by: 1. Underscoring the complex and relational nature of access by conceptualizing three relational perspectives – instrumental, transactional and relational – proposing the latter as a strategy for developing a diplomatic sensitivity to the politics of access; 2. Explicating the political, ethical and emergent nature of access by framing it as an ongoing process of immersion, backstage dramas, and deception; and 3. Offering a number of relational micropractices to help researchers negotiate the complexities of access. We illustrate the challenges of gaining and maintaining access through examples from the literature and from Rafael’s attempts to gain access to carry out fieldwork in a Police Force

    Ethnic entrepreneurs and online home-based businesses: an exploratory study

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    This exploratory, qualitative study considers how online home-based businesses offer opportunities for ethnic entrepreneurs to ‘break out’ of traditional highly competitive and low margin sectors. Previous studies have found a positive association between ethnic minorities’ high levels of entrepreneurship and home computer use in ethnic groups. Despite these associations, previous studies have overlooked the particular opportunities offered by home-based online businesses to ethnic entrepreneurs. The study adopts mixed embeddedness as a theoretical lens to guide interviews with 22 ethnic entrepreneurs who have started online home-based businesses in the UK. We find online home-based businesses offer ethnic entrepreneurs novel opportunities to draw on their ethnic advantages and address the constraints they face. The unique affordances of this type of business allow entrepreneurs to develop the necessary IT skills by self-learning and experimentation and to sub-contract more difficult or time consuming aspects to others. The findings also show that, consistent with the theory of mixed embeddedness, whilst the entrepreneurs are influenced by social, economic and institutional forces, online businesses allow them to exert their own agency and provide opportunities to uniquely shape these forces

    Seven features of safety in maternity units: a framework based on multisite ethnography and stakeholder consultation

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    Background: Reducing avoidable harm in maternity services is a priority globally. As well as learning from mistakes, it is important to produce rigorous descriptions of ‘what good looks like’. Objective: We aimed to characterise features of safety in maternity units and to generate a plain language framework that could be used to guide learning and improvement. Methods: We conducted a multisite ethnography involving 401 hours of non-participant observations 33 semistructured interviews with staff across six maternity units, and a stakeholder consultation involving 65 semistructured telephone interviews and one focus group. Results: We identified seven features of safety in maternity units and summarised them into a framework, named For Us (For Unit Safety). The features include: (1) commitment to safety and improvement at all levels, with everyone involved; (2) technical competence, supported by formal training and informal learning; (3) teamwork, cooperation and positive working relationships; (4) constant reinforcing of safe, ethical and respectful behaviours; (5) multiple problem-sensing systems, used as basis of action; (6) systems and processes designed for safety, and regularly reviewed and optimised; (7) effective coordination and ability to mobilise quickly. These features appear to have a synergistic character, such that each feature is necessary but not sufficient on its own: the features operate in concert through multiple forms of feedback and amplification. Conclusions: This large qualitative study has enabled the generation of a new plain language framework—For Us—that identifies the behaviours and practices that appear to be features of safe care in hospital-based maternity units

    Redefining professional identity: the voice of a language teacher in a context of collaborative learning

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    Following a narrative and biographic approach, in this study, we present the case of an in-service language teacher and her professional learning trajectory in the context of the project ‘Languages and education: constructing and sharing train- ing’. This project aimed at the construction of a collaborative teacher education context for learning and transformation of experiences, views and practices in language education, and involved teachers, teacher educators and researchers. Based on a single case study, the analysis tries to disclose the teacher’s discur- sive displacements as hints of professional transformation while she reinterprets the learning taking place in the collaborative education process. The signs of change are visible in the way she constructs meanings regarding her professional identity, re-identifies her mission as a language teacher and reconsiders her pro- fessional identity. Finally, we reflect upon how collaborative teacher education scenarios may foster teachers’ personal professional learning and renewed self- images
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