5,019 research outputs found

    Resonance line-profile calculations based on hydrodynamical models of cataclysmic variable winds

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    We present synthetic line profiles as predicted by the models of 2-D line- driven disk winds due to Proga, Stone & Drew. We compare the model line profiles with HST observations of the cataclysmic variable IX Vel. The model wind consists of a slow outflow that is bounded on the polar side by a fast stream. We find that these two components of the wind produce distinct spectral features. The fast stream produces profiles which show features consistent with observations. These include the appearance of the P-Cygni shape for a range of inclinations, the location of the maximum depth of the absorption component at velocities less than the terminal velocity, and the transition from absorption to emission with increasing inclination. However the model profiles have too little absorption or emission equivalent width. This quantitative difference between our models and observations is not a surprise because the line-driven wind models predict a mass loss rate that is lower than the rate required by the observations. We note that the model profiles exhibit a double-humped structure near the line center which is not echoed in observations. We identify this structure with a non-negligible redshifted absorption which is formed in the slow component of the wind where the rotational velocity dominates over expansion velocity. We conclude that the next generation of disk wind models, developed for application to CVs, needs to yield stronger wind driving out to larger disk radii than do the present models.Comment: LaTeX, 19 pages, to appear in Ap

    Modeling Vocal Fold Motion with a New Hydrodynamic Semi-Continuum Model

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    Vocal fold (VF) motion is a fundamental process in voice production, and is also a challenging problem for direct numerical computation because the VF dynamics depend on nonlinear coupling of air flow with the response of elastic channels (VF), which undergo opening and closing, and induce internal flow separation. A traditional modeling approach makes use of steady flow approximation or Bernoulli's law which is known to be invalid during VF opening. We present a new hydrodynamic semi-continuum system for VF motion. The airflow is modeled by a quasi-one dimensional continuum aerodynamic system, and the VF by a classical lumped two mass system. The reduced flow system contains the Bernoulli's law as a special case, and is derivable from the two dimensional compressible Navier-Stokes equations. Since we do not make steady flow approximation, we are able to capture transients and rapid changes of solutions, e.g. the double pressure peaks at opening and closing stages of VF motion consistent with experimental data. We demonstrate numerically that our system is robust, and models in-vivo VF oscillation more physically. It is also much simpler than a full two-dimensional Navier-Stokes system.Comment: 27 pages,6 figure

    The Vicarious Liability of Public Officials Under the Civil Rights Act

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    Lawsuit Involving Labor Disputes filed in the United States district courts in 1961 totaled 2,484. In the same year, the number of civil rights cases filed was only 296. Within the next decade, however, the number of civil rights cases filed in the district courts had risen to 6,133 in 1972, a dramatic percentage increase of 1,972. The only area of civil litigation in the federal courts registering a higher tally in 1972 was the closely related area of prisoner petitions. From the briefest perusal of these startling statistics, it becomes readily apparent that civil rights litigation is not only here to stay, but indeed occupies a substantial percentage of the federal courts\u27 civil trial calendar across the countr

    Disproportionate or Excessive Punishments: Is There a Method for Successful Constitutional Challenges?

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    This article will begin with a review of several United States Supreme Court cases, from the emanation of the doctrine in Weems v. United States\u27 to the widely misread and misunderstood case of Harmelin v. Michigan. The article then examines the impact of the Federal Sentencing Guidelines on the federal circuit courts as they relate to claims of disproportionality in prison sentences.\u27 Next, the article explores some of the various state court opinions that have considered the issue of proportionality under federal constitutional guidelines and their own state constitutions. Finally, the article proposes an analytical structure to determine whether a sentence is disproportionate in an individual case

    Delivering organisational adaptation through legislative mechanisms: Evidence from the Adaptation Reporting Power (Climate Change Act 2008)

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    There is increasing recognition that organisations, particularly in key infrastructure sectors, are potentially vulnerable to climate change and extreme weather events, and require organisational responses to ensure they are resilient and adaptive. However, detailed evidence of how adaptation is facilitated, implemented and reported, particularly through legislative mechanisms is lacking. The United Kingdom Climate Change Act (2008), introduced the Adaptation Reporting Power, enabling the Government to direct so-called reporting authorities to report their climate change risks and adaptation plans. We describe the authors' unique role and experience supporting the Department for Environment, Food and Rural Affairs (Defra) during the Adaptation Reporting Power's first round. An evaluation framework, used to review the adaptation reports, is presented alongside evidence on how the process provides new insights into adaptation activities and triggered organisational change in 78% of reporting authorities, including the embedding of climate risk and adaptation issues. The role of legislative mechanisms and risk-based approaches in driving and delivering adaptation is discussed alongside future research needs, including the development of organisational maturity models to determine resilient and well adapting organisations. The Adaptation Reporting Power process provides a basis for similar initiatives in other countries, although a clear engagement strategy to ensure buy-in to the process and research on its long-term legacy, including the potential merits of voluntary approaches, is required

    The Utility of Capsule Endoscopy in Patients under 50 Years of Age with Recurrent Iron Deficiency Anaemia: Is the Juice Worth the Squeeze?

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    Background and Aims. The role of capsule endoscopy (CE) in the <50 years of age patients with iron deficiency anaemia (IDA) remains unclear. We aim to assess its utility in this cohort. Methods. All patients referred for CE for recurrent IDA were included retrospectively. Patients were divided into Group 1 (<50 years) and Group 2 (≥50 years). Results. There were 971 patients with recurrent IDA and 28% belonged to Group 1. The mean age was 40 years in this group with a DY of 28% (). Significant diagnoses included erosions and ulcers (26%; ), small bowel (SB) angioectasia (AE) (10%; ), SB tumours (3%; ), Crohn’s disease (3%; ), SB bowel strictures (1%; ), and SB varices (1%; ). On logistic regression, the presence of diabetes () and the use of warfarin () was associated with increased DY. The DY in Group 2 was 38% which was significantly higher than in Group 1 (). While SB tumours were equally common in both groups, AE was commoner in Group 2 (). Conclusion. A significant proportion of patients <50 years are referred for CE. Although the DY is lower compared to those ≥50 years, significant pathology is found in this age group. CE is advisable in patients <50 years old with recurrent IDA and negative bidirectional endoscopies

    Temperature dependent optical studies of Ti1−x_{1-x}Cox_xO2_2

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    We present the results of Raman and photoluminescence (PL) studies on epitaxial anatase phase Ti1−x_{1-x}Cox_xO2_2 films for xx = 0-0.07, grown by pulsed laser deposition. The low doped system (xx=0.01 and 0.02) shows a Curie temperature of ~700 K in the as-grown state. The Raman spectra from the doped and undoped films confirm their anatase phase. The photoluminescence spectrum is characterized by a broad emission from self-trapped excitons (STE) at 2.3 eV at temperatures below 120 K. This peak is characteristic of the anatase-phase TiO2_2 and shows a small blueshift with increasing doping concentration. In addition to the emission from STE, the Co-doped samples show two emission lines at 2.77 eV and 2.94 eV that are absent in the undoped film indicative of a spin-flip energy.Comment: 8 pages, 4 figure

    Galactic Plane Hα\alpha Surveys: IPHAS & VPHAS+

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    The optical Galactic Plane Hα\alpha surveys IPHAS and VPHAS+ are dramatically improving our understanding of Galactic stellar populations and stellar evolution by providing large samples of stars in short lived, but important, evolutionary phases, and high quality homogeneous photometry and images over the entire Galactic Plane. Here I summarise some of the contributions these surveys have already made to our understanding of a number of key areas of stellar and Galactic astronomy.Comment: 5 pages, 2 figures, refereed proceeding of the "The Universe of Digital Sky Surveys" conference, November 2014, to be published in the Astrophysics and Space Science Proceeding

    Square vortex lattice at anomalously low magnetic fields in electron-doped Nd1.85_{1.85}Ce0.15_{0.15}CuO4_{4}

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    We report here on the first direct observations of the vortex lattice in the bulk of electron-doped Nd1.85_{1.85}Ce0.15_{0.15}CuO4_{4} single crystals. Using small angle neutron scattering, we have observed a square vortex lattice with the nearest-neighbors oriented at 45∘^{\circ} from the Cu-O bond direction, which is consistent with theories based on the d-wave superconducting gap. However, the square symmetry persists down to unusually low magnetic fields. Moreover, the diffracted intensity from the vortex lattice is found to decrease rapidly with increasing magnetic field.Comment: 4 pages, 4 Figures, accepted for publication in Phys. Rev. Let
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