18,838 research outputs found

    Macromia alleghaniensis (Odonata: Macromiidae): New For Michigan, with Clarifications of Northern Records

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    An Alleghany River Cruiser, Macromia alleghaniensis Williamson (Odonata: Macromiidae), collected in Cass County, Michigan on 18 June 2014, represents the first record of the species for the state, as well as the northernmost unequivocal record in North America. Other records north of 40° latitude are clarified and discussed

    Strongly correlated fermions on a kagome lattice

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    We study a model of strongly correlated spinless fermions on a kagome lattice at 1/3 filling, with interactions described by an extended Hubbard Hamiltonian. An effective Hamiltonian in the desired strong correlation regime is derived, from which the spectral functions are calculated by means of exact diagonalization techniques. We present our numerical results with a view to discussion of possible signatures of confinement/deconfinement of fractional charges.Comment: 10 pages, 10 figure

    Towards predicting post-editing productivity

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    Machine translation (MT) quality is generally measured via automatic metrics, producing scores that have no meaning for translators who are required to post-edit MT output or for project managers who have to plan and budget for transla- tion projects. This paper investigates correlations between two such automatic metrics (general text matcher and translation edit rate) and post-editing productivity. For the purposes of this paper, productivity is measured via processing speed and cognitive measures of effort using eye tracking as a tool. Processing speed, average fixation time and count are found to correlate well with the scores for groups of segments. Segments with high GTM and TER scores require substantially less time and cognitive effort than medium or low-scoring segments. Future research involving score thresholds and confidence estimation is suggested

    All-optical memory based on the injection locking bistability of a two-color laser diode

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    We study the injection locking bistability of a specially engineered two-color semiconductor Fabry-Perot laser. Oscillation in the uninjected primary mode leads to a bistability of single mode and two-color equilibria. With pulsed modulation of the injected power we demonstrate an all-optical memory element based on this bistability, where the uninjected primary mode is switched with 35 dB intensity contrast. Using experimental and theoretical analysis, we describe the associated bifurcation structure, which is not found in single mode systems with optical injection.Comment: 5 pages, 5 figure

    Experimental Quantum Process Discrimination

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    Discrimination between unknown processes chosen from a finite set is experimentally shown to be possible even in the case of non-orthogonal processes. We demonstrate unambiguous deterministic quantum process discrimination (QPD) of non-orthogonal processes using properties of entanglement, additional known unitaries, or higher dimensional systems. Single qubit measurement and unitary processes and multipartite unitaries (where the unitary acts non-separably across two distant locations) acting on photons are discriminated with a confidence of 97\geq97% in all cases.Comment: 4 pages, 3 figures, comments welcome. Revised version includes multi-partite QP

    Exact zero-point energy shift in the e(n E)e\otimes (n~E), t(n H)t\otimes (n~H) many modes dynamic Jahn-Teller systems at strong coupling

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    We find the exact semiclassical (strong coupling) zero-point energy shifts applicable to the e(nE)e\otimes (n E) and t(nH)t\otimes (n H) dynamic Jahn-Teller problems, for an arbitrary number nn of discrete vibrational modes simultaneously coupled to one single electronic level. We also obtain an analytical formula for the frequency of the resulting normal modes, which has an attractive and apparently general Slater-Koster form. The limits of validity of this approach are assessed by comparison with O'Brien's previous effective-mode approach, and with accurate numerical diagonalizations. Numerical values obtained for t(nH)t\otimes (n H) with n=8n =8 and coupling constants appropriate to C60_{60}^- are used for this purpose, and are discussed in the context of fullerene.Comment: 20 pages, 4 ps figure

    Negotiating The Interconnections of Sociality, Identity, Fan Activism And Connectivity Within The Twilight Community

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    In my dissertation, “Negotiating the Interconnections of Sociality, Identity, Fan Activism and Connectivity within the Twilight Community”, I examine the ways in which women employed a shared interest in a cultural text to establish meaningful social relationships with other fans. Rather than focusing solely on consumptive pleasure, these fans of the Twilight series utilized the intense popularity of the franchise to engage in charitable activities. Through these common threads of identity, community, virtual technologies, and charity, I contend that the Twilight fandom represents a new form of fan community, which is trending upward and creating an impact beyond the traditional sphere of fandom. The internet and virtual technologies continue to increase the interconnectedness between people, and the ways in which experiences –online and offline—intermingle and flow back and forth to create vibrant fan communities that impact the world with both consumptive pleasure and altruistic intentions. As such, it becomes relevant to understand the ways in which fandom and the ensuing activities are enacted and experienced by people in a contemporary, technologically mediated community

    Systematic Errors in the Estimation of Black Hole Masses by Reverberation Mapping

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    The mass of the central black hole in many active galactic nuclei has been estimated on the basis of the assumption that the dynamics of the broad emission line gas are dominated by the gravity of the black hole. The most commonly-employed method is to estimate a characteristic size-scale rr_* from reverberation mapping experiments and combine it with a characteristic velocity vv_* taken from the line profiles; the inferred mass is then estimated by rv2/Gr_* v_*^2/G. We critically discuss the evidence supporting the assumption of gravitational dynamics and find that the arguments are still inconclusive. We then explore the range of possible systematic error if the assumption of gravitational dynamics is granted. Inclination relative to a flattened system may cause a systematic underestimate of the central mass by a factor (h/r)2\sim (h/r)^2, where h/rh/r is the aspect ratio of the flattening. The coupled effects of a broad radial emissivity distribution, an unknown angular radiation pattern of line emission, and sub-optimal sampling in the reverberation experiment can cause additional systematic errors as large as a factor of 3 or more in either direction.Comment: 19 pages, 4 figures, AASLaTeX, accepted by Ap

    Changing social contracts in climate-change adaptation

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    Risks from extreme weather events are mediated through state, civil society and individual action 1 , 2 . We propose evolving social contracts as a primary mechanism by which adaptation to climate change proceeds. We use a natural experiment of policy and social contexts of the UK and Ireland affected by the same meteorological event and resultant flooding in November 2009. We analyse data from policy documents and from household surveys of 356 residents in western Ireland and northwest England. We find significant differences between perceptions of individual responsibility for protection across the jurisdictions and between perceptions of future risk from populations directly affected by flooding events. These explain differences in stated willingness to take individual adaptive actions when state support retrenches. We therefore show that expectations for state protection are critical in mediating impacts and promoting longer-term adaptation. We argue that making social contracts explicit may smooth pathways to effective and legitimate adaptation
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