2,601 research outputs found

    Another Flattened Dark Halo: Plar Ring Galaxy A0136-0801

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    Knowledge of the shape of dark matter halos is critical to our understanding of galaxy formation, dynamics, and of the nature of dark matter itself. Polar ring galaxies (PRGs) --- early-type galaxies defined by their outer rings of gas, dust and stars on orbits nearly perpendicular to those of the central host --- provide a rare probe of the vertical-to-radial axis ratio (qρ=c/a) (q_{\rho} = c/a) of dark halos. We present a Fabry-Perot velocity field for the Hα\alpha gas in the kinematically-confirmed PRG \gal. By comparing ring orbits evolved in a generalized mass model to the observed ring velocity field and morphology of \gal, we conclude that qρ0.5q_\rho \sim 0.5 and rule out a spherical geometry.Comment: uuencoded gz-compressed file with figures include

    Rocket exhaust plume computer program improvement. Volume 1: Summary: Method of characteristics nozzle and plume programs

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    A summary is presented of the various documents that discuss and describe the computer programs and analysis techniques which are available for rocket nozzle and exhaust plume calculations. The basic method of characteristics program is discussed, along with such auxiliary programs as the plume impingement program, the plot program and the thermochemical properties program

    Comparing families of dynamic causal models

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    Mathematical models of scientific data can be formally compared using Bayesian model evidence. Previous applications in the biological sciences have mainly focussed on model selection in which one first selects the model with the highest evidence and then makes inferences based on the parameters of that model. This “best model” approach is very useful but can become brittle if there are a large number of models to compare, and if different subjects use different models. To overcome this shortcoming we propose the combination of two further approaches: (i) family level inference and (ii) Bayesian model averaging within families. Family level inference removes uncertainty about aspects of model structure other than the characteristic of interest. For example: What are the inputs to the system? Is processing serial or parallel? Is it linear or nonlinear? Is it mediated by a single, crucial connection? We apply Bayesian model averaging within families to provide inferences about parameters that are independent of further assumptions about model structure. We illustrate the methods using Dynamic Causal Models of brain imaging data

    Lupus-TR-3b: A Low-Mass Transiting Hot Jupiter in the Galactic Plane?

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    We present a strong case for a transiting Hot Jupiter planet identified during a single-field transit survey towards the Lupus Galactic plane. The object, Lupus-TR-3b, transits a V=17.4 K1V host star every 3.91405d. Spectroscopy and stellar colors indicate a host star with effective temperature 5000 +/- 150K, with a stellar mass and radius of 0.87 +/- 0.04M_sun and 0.82 +/- 0.05R_sun, respectively. Limb-darkened transit fitting yields a companion radius of 0.89 +/- 0.07R_J and an orbital inclination of 88.3 +1.3/-0.8 deg. Magellan 6.5m MIKE radial velocity measurements reveal a 2.4 sigma K=114 +/- 25m/s sinusoidal variation in phase with the transit ephemeris. The resulting mass is 0.81 +/- 0.18M_J and density 1.4 +/- 0.4g/cm^3. Y-band PANIC image deconvolution reveal a V>=21 red neighbor 0.4'' away which, although highly unlikely, we cannot conclusively rule out as a blended binary with current data. However, blend simulations show that only the most unusual binary system can reproduce our observations. This object is very likely a planet, detected from a highly efficient observational strategy. Lupus-TR-3b constitutes the faintest ground-based detection to date, and one of the lowest mass Hot Jupiters known.Comment: 4 pages, 4 figures, accepted for publication in ApJ

    High eccentricity planets from the Anglo-Australian Planet Search

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    We report Doppler measurements of the stars HD187085 and HD20782 which indicate two high eccentricity low-mass companions to the stars. We find HD187085 has a Jupiter-mass companion with a ~1000d orbit. Our formal `best fit' solution suggests an eccentricity of 0.47, however, it does not sample the periastron passage of the companion and we find that orbital solutions with eccentricities between 0.1 and 0.8 give only slightly poorer fits (based on RMS and chi^2) and are thus plausible. Observations made during periastron passage in 2007 June should allow for the reliable determination of the orbital eccentricity for the companion to HD187085. Our dataset for HD20782 does sample periastron and so the orbit for its companion can be more reliably determined. We find the companion to HD20782 has M sin i=1.77+/-0.22M_JUP, an orbital period of 595.86+/-0.03d and an orbit with an eccentricity of 0.92+/-0.03. The detection of such high-eccentricity (and relatively low velocity amplitude) exoplanets appears to be facilitated by the long-term precision of the Anglo-Australian Planet Search. Looking at exoplanet detections as a whole, we find that those with higher eccentricity seem to have relatively higher velocity amplitudes indicating higher mass planets and/or an observational bias against the detection of high eccentricity systems.Comment: to appear in MNRA

    Predictive indicators for revisional surgery in nasal reconstruction after Mohs surgery

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    Background: Reconstruction of nasal lesions is complex due to the topography, mobile free margins and borders of anatomical subunits. Reconstructive challenges can lead to multiple revisional surgeries to achieve the final aesthetic result. This study aimed to evaluate risk factors and predictors of revisional surgery in patients undergoing reconstruction after Mohs micrographic surgery for nasal tumours. Methods: This was a prospective cohort study from April 2, 2008 to February 26, 2019. The study population included all consecutive patients who underwent Mohs micrographic surgery for nasal skin cancer. Resection and reconstruction of nasal skin cancer was performed by the Mohs team. Results: A total of 988 cases met our study inclusion criteria with 64 (6.5%) cases requiring unplanned surgical revision. Revision rates were highest in the ala (9.0%, p < 0.05) and complex anatomical subunits (16.7%, p < 0.0001). In contrast, revision rates for dorsum lesions were lowest (1.8%, p < 0.001). In terms of reconstructive modalities, local flaps resulted in significantly higher rates of revision when compared to grafts (relative risk, 2.37; 95% CI, 1.15–5.0; p < 0.01). In terms of histological diagnosis, squamous cell carcinoma had significantly higher revision rates when compared to basal cell carcinoma (p < 0.05). Conclusions: To our knowledge, this is the first study to report the risk factors and predictors of revision surgery in patients undergoing MMS for nasal tumours. This study highlights that the reconstructive modality utilised affects the functional and cosmetic outcome of MMS. We note that ala complex subunit lesions, squamous cell carcinoma and flap reconstruction were associated with an increased risk of revision after Mohs reconstruction of nasal lesions. Level of evidence: Level III, risk/prognostic; therapeutic study. Trial registration number: (Ref: PLA-19-20_A03) 04/02/2020

    Phase-resolved Crab Studies with a Cryogenic TES Spectrophotometer

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    We are developing time- and energy-resolved near-IR/optical/UV photon detectors based on sharp superconducting-normal transition edges in thin films. We report observations of the Crab pulsar made during prototype testing at the McDonald 2.7m telescope with a fiber-coupled transition-edge sensor (TES) system. These data show substantial (d[alpha]~0.3), rapid variations in the spectral index through the pulse profile, with a strong phase-varying IR break across our energy band. These variations correlate with X-ray spectral variations, but no single synchrotron population can account for the full Spectral Energy Distribution (SED). We also describe test spectrophotopolarimetry observations probing the energy dependence of the polarization sweep; this may provide a new key to understanding the radiating particle population.Comment: 12 pages, 10 figures -- to appear in ApJ V56

    A Check-List Of The Mecoptera Of The World

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    All known species of recent Mecoptera are cataloguedreference is given to original descriptions; and known distributions are recorded. New names for two junior homonyms (Panorpa issiki = Panorpa acuta Issiki & Cheng, and Panorpa banksiana = Panorpa interrupta Banks) are included, and one new synonymy (Panorpa galloisi Miyake = Panorpa cornigera MacLachlan) is noted.Citamos de todas as espécies conhecidas de Mecoptera, com as citações bibliográficas originais e respectiva distribuição geográfica. Dados sobre a diversidade das famílias, gêneros e espécies são apresentados, bem como notadas duas homonímias e uma sinonímia
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