3,549 research outputs found

    Irrational War and Constitutional Design: A Reply to Professors Nzelibe and Yoo

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    This Reply proceeds as follows. Part I outlines the argument of the Nzelibe and Yoo paper. Part II considers their principal-agent analysis in the context of the American political system. Part III elaborates on the democratic peace literature, demonstrating that it does not support the conclusions that they draw. Part IV addresses the argument that we are in a new strategic situation, such that old rules ought not apply. Part V concludes

    A note on preservation of languages by transducers

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    An error in a previous paper is corrected. The rectified version involves pushdown transducers with accepting states instead of pushdown transducers. Some properties of pushdown transducers with accepting states are then noted

    Feedback from massive stars at low metallicities : MUSE observations of N44 and N180 in the Large Magellanic Cloud

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    Accepted for publication in MNRAS, 27 pages, 21 figuresWe present MUSE integral field data of two HII region complexes in the Large Magellanic Cloud (LMC), N44 and N180. Both regions consist of a main superbubble and a number of smaller, more compact HII regions that formed on the edge of the superbubble. For a total of 11 HII regions, we systematically analyse the radiative and mechanical feedback from the massive O-type stars on the surrounding gas. We exploit the integral field property of the data and the coverage of the HeIIλ\lambda5412 line to identify and classify the feedback-driving massive stars, and from the estimated spectral types and luminosity classes we determine the stellar radiative output in terms of the ionising photon flux Q0Q_{0}. We characterise the HII regions in terms of their sizes, morphologies, ionisation structure, luminosity and kinematics, and derive oxygen abundances via emission line ratios. We analyse the role of different stellar feedback mechanisms for each region by measuring the direct radiation pressure, the pressure of the ionised gas, and the pressure of the shock-heated winds. We find that stellar winds and ionised gas are the main drivers of HII region expansion in our sample, while the direct radiation pressure is up to three orders of magnitude lower than the other terms. We relate the total pressure to the star formation rate per unit area, ΣSFR\Sigma_{SFR}, for each region and find that stellar feedback has a negative effect on star formation, and sets an upper limit to ΣSFR\Sigma_{SFR} as a function of increasing pressure.Peer reviewe

    Exploring ways to overcome barriers to mammography uptake and retention among South Asian immigrant women

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    South Asians comprise one of the fastest growing immigrant groups in North America. Evidence indicates that South Asian (SA) immigrant women are vulnerable to low rates of breast cancer screening. Yet, there is a dearth of knowledge pertaining to socio-culturally tailored strategies to guide the uptake of screening mammography in the SA community. In 2010, the authors conducted semi-structured focus groups to elicit perspectives of health and social service professionals on possible solutions to barriers identified by SA immigrant women in a recent study conducted in the Greater Toronto Area. Thirty-five health and social services staff members participated in five focus groups. The discussions were audio taped and detailed field notes were taken. All collected data was transcribed verbatim and thematic analysis was conducted using techniques of constant comparison within and across the group discussions. Three dominant themes were identified: 1) “Target and Tailor” focused on awareness-raising through multiple direct and indirect modes or approaches with underlying shared processes of involving men and the whole family, use of first language, and learning from peers; 2) “Enhancing Access to Services” included a focus on ‘adding ancillary services’ and ‘reinforcement of existing services’ including expansion to a one-stop model; and 3) “Meta-Characteristics” centred on providing ‘multi-pronged’ approaches to reach the community, and ‘sustainability’ of initiatives by addressing structural barriers of adequate funding, healthcare provider mix, inter-sectoral collaboration, and community voice. The findings simultaneously shed light on the grass-roots practical strategies and the system level changes in order to develop efficient programmes for the uptake of mammography among SA immigrant women. The parallel focus on the “Target and Tailor” and “Enhancing Access to Services” calls for coordination at the policy level so that multiple sectors work jointly to streamline resources, or meta-characteristics.The project funds were provided by the Canadian Cancer Society, Ontario Division

    Interpretations of Presburger Arithmetic in Itself

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    Presburger arithmetic PrA is the true theory of natural numbers with addition. We study interpretations of PrA in itself. We prove that all one-dimensional self-interpretations are definably isomorphic to the identity self-interpretation. In order to prove the results we show that all linear orders that are interpretable in (N,+) are scattered orders with the finite Hausdorff rank and that the ranks are bounded in terms of the dimension of the respective interpretations. From our result about self-interpretations of PrA it follows that PrA isn't one-dimensionally interpretable in any of its finite subtheories. We note that the latter was conjectured by A. Visser.Comment: Published in proceedings of LFCS 201

    Location of the active site for enzyme-adenylate formation in DNA ligases.

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    The Pillars of Creation revisited with MUSE: gas kinematics and high-mass stellar feedback traced by optical spectroscopy

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    This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.Integral field unit (IFU) data of the iconic Pillars of Creation in M16 are presented. The ionization structure of the pillars was studied in great detail over almost the entire visible wavelength range, and maps of the relevant physical parameters, e.g. extinction, electron density, electron temperature, line-of-sight velocity of the ionized and neutral gas are shown. In agreement with previous authors, we find that the pillar tips are being ionized and photoevaporated by the massive members of the nearby cluster NGC 6611. They display a stratified ionization structure where the emission lines peak in a descending order according to their ionization energies. The IFU data allowed us to analyse the kinematics of the photoevaporative flow in terms of the stratified ionization structure, and we find that, in agreement with simulations, the photoevaporative flow is traced by a blueshift in the position-velocity profile. The gas kinematics and ionization structure have allowed us to produce a sketch of the 3D geometry of the Pillars, positioning the pillars with respect to the ionizing cluster stars. We use a novel method to detect a previously unknown bipolar outflow at the tip of the middle pillar and suggest that it has an embedded protostar as its driving source. Furthermore we identify a candidate outflow in the leftmost pillar. With the derived physical parameters and ionic abundances, we estimate a mass-loss rate due to the photoevaporative flow of 70 M⊙ Myr−1 which yields an expected lifetime of approximately 3 Myr.Peer reviewe

    A probable Keplerian disk feeding an optically revealed massive young star.

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    The canonical picture of star formation involves disk-mediated accretion, with Keplerian accretion disks and associated bipolar jets primarily observed in nearby, low-mass young stellar objects (YSOs). Recently, rotating gaseous structures and Keplerian disks have been detected around several massive (M > 8 M ) YSOs (MYSOs) , including several disk-jet systems . All the known MYSO systems are in the Milky Way, and all are embedded in their natal material. Here we report the detection of a rotating gaseous structure around an extragalactic MYSO in the Large Magellanic Cloud. The gas motion indicates that there is a radial flow of material falling from larger scales onto a central disk-like structure. The latter exhibits signs of Keplerian rotation, so that there is a rotating toroid feeding an accretion disk and thus the growth of the central star. The system is in almost all aspects comparable to Milky Way high-mass YSOs accreting gas from a Keplerian disk. The key difference between this source and its Galactic counterparts is that it is optically revealed rather than being deeply embedded in its natal material as is expected of such a massive young star. We suggest that this is the consequence of the star having formed in a low-metallicity and low-dust content environment. Thus, these results provide important constraints for models of the formation and evolution of massive stars and their circumstellar disks. [Abstract copyright: © 2023. The Author(s).
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