13,053 research outputs found

    Loran-C approach guidance project current status

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    There are four areas of work in the Loran-C flight test project. Current results provide performance data on the effects of Signal Noise Ratio (SNR) on the dynamic performance of the receiver filters for Loran-C data, and data on Loran-C grid deformation at a microscale of 100 meters. The Loran-C receiver provides a line of position (LOP) Master and Slave transmitter at an angle 0 to magnetic north. No transformation to latitude-longitude reference frame is required since this is the major source of Loran-C navigation errors. A local coordinate frame is established centered at touchdown point on the runway with directions along and across the runway. A Loran-C data collection system was set up. The Loran-C data are sent directly to an Apple II computer with a 12 inch monitor. The effect of SNR on Loran-C precision is shown for two receiver filters of different frequency response. A set of ground level static readings of touchdown was taken around Hanscom Field and transferred to an accurate detailed layout drawing; this showed local distortions of the average touchdown values

    Homogeneous cosmologies and the Maupertuis-Jacobi principle

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    A recent work showing that homogeneous and isotropic cosmologies involving scalar fields are equivalent to the geodesics of certain effective manifolds is generalized to the non-minimally coupled and anisotropic cases. As the Maupertuis-Jacobi principle in classical mechanics, such result permits us to infer some dynamical properties of cosmological models from the geometry of the associated effective manifolds, allowing us to go a step further in the study of cosmological dynamics. By means of some explicit examples, we show how the geometrical analysis can simplify considerably the dynamical analysis of cosmological models.Comment: 5 page

    Incorporation of Spacetime Symmetries in Einstein's Field Equations

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    In the search for exact solutions to Einstein's field equations the main simplification tool is the introduction of spacetime symmetries. Motivated by this fact we develop a method to write the field equations for general matter in a form that fully incorporates the character of the symmetry. The method is being expressed in a covariant formalism using the framework of a double congruence. The basic notion on which it is based is that of the geometrisation of a general symmetry. As a special application of our general method we consider the case of a spacelike conformal Killing vector field on the spacetime manifold regarding special types of matter fields. New perspectives in General Relativity are discussed.Comment: 41 pages, LaTe

    Higgs Inflation as a Mirage

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    We discuss a simple unitarization of Higgs inflation that is genuinely weakly coupled up to Planckian energies. A large non-minimal coupling between the Higgs and the Ricci curvature is induced dynamically at intermediate energies, as a simple ratio of mass scales. Despite not being dominated by the Higgs field, inflationary dynamics simulates the `Higgs inflation' one would get by blind extrapolation of the low-energy effective Lagrangian, at least qualitatively. Hence, Higgs inflation arises as an approximate `mirage' picture of the true dynamics. We further speculate on the generality of this phenomenon and show that, if Higgs-inflation arises as an effective description, the details of the UV completion are necessary to extract robust quantitative predictions.Comment: 21 pages, 2 figure

    In search of 'community': a critical review of community mental health services for women in African settings

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    Community is deemed a central resource for the improvement of health, across disciplines, contexts and conditions. However, what is meant by this term is rarely critically explored. In Global Mental Health, considerable efforts in recent years have been directed towards scaling up ‘community’ approaches, with variable success, creating the need to better understand approaches to its use. Our study contributes to this need, through a critical review of studies engaging with the term ‘community’ in relation to women’s mental health services in African settings. Our review explored 30 peer-reviewed articles from the past 15 years, which were systematically evaluated for quality of evidence. Studies were then analysed using a blend of conventional and directed content analysis to unpack perspectives on the term’s use in intervention and phenomenological studies. We identified four broad categories of community: (1) place (shared geographical location or institutional affiliation), (2) practice (belongingness to a shared activity or profession), (3) symbols (meanings and experiences associated with shared community life) and (4) identity (diagnostic identity around a mental health condition). Analysis identified community of place as the most common primary focus of interest across the sample, with 80% of papers referencing this dimension. We noted that in studies where communities of practice were the focus, this was in relation to leveraging local knowledge to inform or support service delivery of intervention programmes, often designed by outsiders. Implications for future policy and mental health services research are discussed

    SN 2013df, a double-peaked IIb supernova from a compact progenitor and an extended H envelope

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    Optical observations of the type IIb SN 2013df from a few days to about 250 days after explosion are presented. These observations are complemented with UV photometry taken by \textit{SWIFT} up to 60 days post-explosion. The double-peak optical light curve is similar to those of SNe 1993J and 2011fu although with different decline and rise rates. From the modelling of the bolometric light curve, we have estimated that the total mass of synthesised 56^{56}Ni in the explosion is ∼0.1\sim0.1 M⊙_{\odot}, while the ejecta mass is 0.8−1.40.8-1.4 M⊙_{\odot} and the explosion energy 0.4−1.2×10510.4-1.2 \times 10^{51}erg. In addition, we have estimated a lower limit to the progenitor radius ranging from 64−16964-169 R⊙R_{\odot}. The spectral evolution indicates that SN 2013df had a hydrogen envelope similar to SN 1993J (∼0.2\sim 0.2 M⊙_{\odot}). The line profiles in nebular spectra suggest that the explosion was asymmetric with the presence of clumps in the ejecta, while the [O\,{\sc i}] λ\lambdaλ\lambda63006300, 63646364 luminosities, may indicate that the progenitor of SN 2013df was a relatively low mass star ( ∼12−13\sim 12-13 M⊙_{\odot}).Comment: 18 pages, 11 figures, 9 tables, accepted for publication in MNRA

    The Suprafroth (Superconducting Froth)

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    The structure and dynamics of froths have been subjects of intense interest due to the desire to understand the behaviour of complex systems where topological intricacy prohibits exact evaluation of the ground state. The dynamics of a traditional froth involves drainage and drying in the cell boundaries, thus it is irreversible. We report a new member to the froths family: suprafroth, in which the cell boundaries are superconducting and the cell interior is normal phase. Despite very different microscopic origin, topological analysis of the structure of the suprafroth shows that statistical von Neumann and Lewis laws apply. Furthermore, for the first time in the analysis of froths there is a global measurable property, the magnetic moment, which can be directly related to the suprafroth structure. We propose that this suprafroth is a new, model system for the analysis of the complex physics of two-dimensional froths

    Explosion of a massive, He-rich star at z=0.16

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    We present spectroscopic and photometric data of the peculiar SN 2001gh, discovered by the 'Southern inTermediate Redshift ESO Supernova Search' (STRESS) at a redshift z=0.16. SN 2001gh has relatively high luminosity at maximum (M_B = -18.55 mag), while the light curve shows a broad peak. An early-time spectrum shows an almost featureless, blue continuum with a few weak and shallow P-Cygni lines that we attribute to HeI. HeI lines remain the only spectral features visible in a subsequent spectrum, obtained one month later. A remarkable property of SN 2001gh is the lack of significant spectral evolution over the temporal window of nearly one month separating the two spectra. In order to explain the properties of SN 2001gh, three powering mechanism are explored, including radioactive decays of a moderately large amount of 56Ni, magnetar spin-down, and interaction of SN ejecta with circumstellar medium. We favour the latter scenario, with a SN Ib wrapped in a dense, circumstellar shell. The fact that no models provide an excellent fit with observations, confirms the troublesome interpretation of the nature of SN 2001gh. A rate estimate for SN 2001gh-like event is also provided, confirming the intrinsic rarity of these objects.Comment: 11 pages, 8 figures, 3 tables. Accepted by MNRA

    Educators in the Catholic Intellectual Tradition

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    This book contains a collection of studies of prominent educators who have made significant contributions to handing on the Catholic intellectual tradition in the United States. These men and women have enriched this tradition by careful attention to educational theories and methods that find their origin in the Jewish and Christian past. Ancient Israel was assiduous in handing on the Torah or Law, the prophets dramatically called people back to the practices of the covenant, and the sages gave practical advice for everyday living. The Acts of the Apostles and the Letters of Paul chronicle the careful attention to safeguarding and transmitting the teachings in the early apostolic Christian communities. Contributors to this tradition in the past three centuries have been mainly European scholars. However, in the past two centuries educators in the United States have made notable contributions to the task of handing on the Catholic intellectual tradition. Table of contents: John Lancaster Spalding: prelate and philosopher of Catholic education / Lucinda A. Nolan -- Edward Pace: pioneer psychologist, philosopher, and religious educator / John L. Elias -- Thomas E. Shields: progressive Catholic religious educator / John L. Elias -- George Johnson: policy maker for Catholic education / John L. Elias -- Virgil Michel: prophet of liturgical education and reform / Jacqueline Parascandola -- Sister M. Rosalia Walsh and the parish catechetical apostolate / Lucinda A. Nolan -- Jacques Maritain and his contribution to the philosophy of Catholic education in America / Luz M. Ibarra -- Neil G. McCluskey: a public voice for Catholic education / Harold D. Horell -- Mary Perkins Ryan: visionary in modern Catholic religious education / Ann M. Heekin -- Shaping the Christian century: the vision of Gerald Sloyan / Philip A. Franco.https://digitalcommons.sacredheart.edu/shupress_bks/1023/thumbnail.jp

    Moderately Luminous type II Supernovae

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    Core-collapse Supernovae (CC-SNe) descend from progenitors more massive than about 8 Msun. Because of the young age of the progenitors, the ejecta may eventually interact with the circumstellar medium (CSM) via highly energetic processes detectable in the radio, X-ray, ultraviolet (UV) and, sometimes, in the optical domains. In this paper we present ultraviolet, optical and near infrared observations of five type II SNe, namely SNe 2009dd, 2007pk, 2010aj, 1995ad, and 1996W. Together with few other SNe they form a group of moderately luminous type II events. We collected photometry and spectroscopy with several telescopes in order to construct well-sampled light curves and spectral evolutions from the photospheric to the nebular phases. Both photometry and spectroscopy indicate a degree of heterogeneity in this sample. The light curves have luminous peak magnitudes (−16.95<MB<−18.70-16.95<M_{B}<-18.70). The ejected masses of ^56\ni for three SNe span a wide range of values (2.8×10−22.8\times10^{-2}Msun<<M(\ni)<1.4×10−1<1.4\times10^{-1}Msun), while for a fourth (SN2010aj) we could determine a stringent upper limit (7×10−37\times10^{-3}Msun). Clues of interaction, such as the presence of high velocity (HV) features of the Balmer lines, are visible in the photospheric spectra of SNe 2009dd and 1996W. For SN2007pk we observe a spectral transition from a type IIn to a standard type II SN. Modelling the observations of SNe 2009dd, 2010aj and 1995ad with radiation hydrodynamics codes, we infer kinetic plus thermal energies of about 0.2-0.5 foe, initial radii of 2-5×1013\times10^{13} cm and ejected masses of ∼\sim5.0-9.5 Msun. These values suggest moderate-mass, super-asymptotic giant branch (SAGB) or red super-giants (RSG) stars as SN precursors, in analogy with other luminous type IIP SNe 2007od and 2009bw.Comment: 28 pages, 27 fig, accepted by A&A, 3 pages of online material, abstract abridged. revised significantly with respect to the previous versio
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