2,216 research outputs found

    A Fast Gradient and Function Sampling Method for Finite Max-Functions

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    This paper tackles the unconstrained minimization of a class of nonsmooth and nonconvex functions that can be written as finite max-functions. A gradient and function-based sampling method is proposed which, under special circumstances, either moves superlinearly to a minimizer of the problem of interest or superlinearly improves the optimality certificate. Global and local convergence analysis are presented, as well as illustrative examples that corroborate and elucidate the obtained theoretical results

    The Lesser Role of Shear in Galactic Star Formation Insight from the Galactic Ring Survey

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    We analyze the role played by shear in regulating star formation in the Galaxy on the scale of individual molecular clouds. The clouds are selected from the 13 CO J = 1-0 line of the Galactic Ring Survey. For each cloud, we estimate the shear parameter which describes the ability of density perturbations to grow within the cloud. We find that for almost all molecular clouds considered, there is no evidence that shear is playing a significant role in opposing the effects of self-gravity. We also find that the shear parameter of the clouds does not depend on their position in the Galaxy. Furthermore, we find no correlations between the shear parameter of the clouds with several indicators of their star formation activity. No significant correlation is found between the shear parameter and the star formation efficiency of the clouds which is measured using the ratio of the massive young stellar objects luminosities, measured in the Red MSX survey, to the cloud mass. There are also no significant correlations between the shear parameter and the fraction of their mass that is found in denser clumps which is a proxy for their clump formation efficiency, nor with their level of fragmentation expressed in the number of clumps per unit mass. Our results strongly suggest that shear is playing only a minor role in affecting the rates and efficiencies at which molecular clouds convert their gas into dense cores and thereafter into stars. © 2012. The American Astronomical Society. All rights reserved

    UV to radio centimetric spectral energy distributions of optically-selected late-type galaxies in the Virgo cluster

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    We present a multifrequency dataset for an optically-selected, volume-limited, complete sample of 118 late-type galaxies (>= S0a) in the Virgo cluster. The database includes UV, visible, near-IR, mid-IR, far-IR, radio continuum photometric data as well as spectroscopic data of Halpha, CO and HI lines, homogeneously reduced, obtained from our own observations or compiled from the literature. Assuming the energy balance between the absorbed stellar light and that radiated in the IR by dust, we calibarte an empirical attenuation law suitable for correcting photometric and spectroscopic data of normal galaxies. The data, corrected for internal extinction, are used to construct the spectral energy distribution (SED) of each individual galaxy, and combined to trace the median SED of galaxies in various classes of morphological type and luminosity. Low-luminosity, dwarf galaxies have on average bluer stellar continua and higher far-IR luminosities per unit galaxy mass than giant, early-type spirals. If compared to nearby starburst galaxies such as M82 and Arp 220, normal spirals have relatively similar observed stellar spectra but 10-100 times lower IR luminosities. The temperature of the cold dust component increases with the far-IR luminosity, from giant spirals to dwarf irregulars. The SED are used to separate the stellar emission from the dust emission in the mid-IR regime. We show that the contribution of the stellar emission at 6.75 micron to the total emission of galaxies is generally important, from ~ 80% in Sa to ~ 20% in Sc.Comment: 31 pages, 12 figures, 12 tables. Fig 2 avaliable at (http://goldmine.mib.infn.it/papers/isosed.html). Accepted for publication on A&

    A Deep WSRT 1.4 GHz Radio Survey of the Spitzer Space Telescope FLSv Region

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    The First Look Survey (FLS) is the first scientific product to emerge from the Spitzer Space Telescope. A small region of this field (the verification strip) has been imaged very deeply, permitting the detection of cosmologically distant sources. We present Westerbork Synthesis Radio Telescope (WSRT) observations of this region, encompassing a ~1 sq. deg field, centred on the verification strip (J2000 RA=17:17:00.00, DEC=59:45:00.000). The radio images reach a noise level of ~ 8.5 microJy/beam - the deepest WSRT image made to date. We summarise here the first results from the project, and present the final mosaic image, together with a list of detected sources. The effect of source confusion on the position, size and flux density of the faintest sources in the source catalogue are also addressed. The results of a serendipitous search for HI emission in the field are also presented. Using a subset of the data, we clearly detect HI emission associated with four galaxies in the central region of the FLSv. These are identified with nearby, massive galaxies.Comment: 9 pages, 6 figures (fig.3 in a separate gif file). Accepted for publication in A&A. The full paper and the related material can be downloaded from http://www.astron.nl/wsrt/WSRTsurveys/WFLS

    The Mid-Infrared Spectra of Normal Galaxies

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    The mid-infrared spectra (2.5 to 5 and 5.7 to 11.6 mu) obtained by ISO-PHOT reveal the interstellar medium emission from galaxies powered by star formation to be strongly dominated by the aromatic features at 6.2, 7.7, 8.6 and 11.3 mu. Additional emission appears in-between the features, and an underlying continuum is clearly evident at 3-5 mu. This continuum would contribute about a third of the luminosity in the 3 to 13 mu range. The features together carry 5 to 30% of the 40-to-120 mu `FIR' luminosity. The relative fluxes in individual features depend very weakly on galaxy parameters such as the far-infrared colors, direct evidence that the emitting particles are not in thermal equilibrium. The dip at 10 mu is unlikely to result from silicate absorption, since its shape is invariant among galaxies. The continuum component has a f_nu \~ nu^{0.65} shape between 3 and 5 mu and carries 1 to 4% of the FIR luminosity; its extrapolation to longer wavelengths falls well below the spectrum in the 6 to 12 mu range. This continuum component is almost certainly of non-stellar origin, and is probably due to fluctuating grains without aromatic features. The spectra reported here typify the integrated emission from the interstellar medium of the majority of star-forming galaxies, and could thus be used to obtain redshifts of highly extincted galaxies up to z=3 with SIRTF.Comment: 10 pages, 2 figures, uses AAS LaTeX; to appear in the Astrophysical Journal Letter

    The impact of a multidisciplinary self-care management program on quality of life, self-care, adherence to anti-hypertensive therapy, glycemic control, and renal function in diabetic kidney disease: A Cross-over Study Protocol.

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    Diabetic kidney disease, a global health issue, remains associated with high morbidity and mortality. Previous research has shown that multidisciplinary management of chronic disease can improve patient outcomes. The effect of multidisciplinary self-care management on quality of life and renal function of patients with diabetic kidney disease has not yet been well established. The aim of this study is to evaluate the impact of a multidisciplinary self-care management program on quality of life, self-care behavior, adherence to anti-hypertensive treatment, glycemic control, and renal function of adults with diabetic kidney disease. A uniform balanced cross-over design is used, with the objective to recruit 40 adult participants with diabetic kidney disease, from public and private out-patient settings in French speaking Switzerland. Participants are randomized in equal number into four study arms. Each participant receives usual care alternating with the multidisciplinary self- care management program. Each treatment period lasts three months and is repeated twice at different time intervals over 12 months depending on the cross-over arm. The multidisciplinary self-care management program is led by an advanced practice nurse and adds nursing and dietary consultations and follow-ups, to the habitual management provided by the general practitioner, the nephrologist and the diabetologist. Data is collected every three months for 12 months. Quality of life is measured using the Audit of Diabetes-Dependent Quality of Life scale, patient self-care behavior is assessed using the Revised Summary of Diabetes Self-Care Activities, and adherence to anti-hypertensive therapy is evaluated using the Medication Events Monitoring System. Blood glucose control is measured by the glycated hemoglobin levels and renal function by serum creatinine, estimated glomerular filtration rate and urinary albumin/creatinine ratio. Data will be analyzed using STATA version 14. The cross-over design will elucidate the responses of individual participant to each treatment, and will allow us to better evaluate the use of such a design in clinical settings and behavioral studies. This study also explores the impact of a theory-based nursing practice and its implementation into a multidisciplinary context. ClinicalTrials.gov identifier: NCT01967901 , registered on the 18th of October 2013

    ATLAS Probe: Breakthrough Science of Galaxy Evolution, Cosmology, Milky Way, and the Solar System

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    Astrophysics Telescope for Large Area Spectroscopy Probe is a concept for a National Aeronautics and Space Administration probe-class space mission that will achieve ground-breaking science in the fields of galaxy evolution, cosmology, Milky Way, and the Solar System. It is the follow-up space mission to Wide Field Infrared Survey Telescope (WFIRST), boosting its scientific return by obtaining deep 1–4 μm slit spectroscopy for ∼70% of all galaxies imaged by the ∼2 000 deg^2 WFIRST High Latitude Survey at z > 0.5. Astrophysics Telescope for Large Area Spectroscopy will measure accurate and precise redshifts for ∼200 M galaxies out to z < 7, and deliver spectra that enable a wide range of diagnostic studies of the physical properties of galaxies over most of cosmic history. Astrophysics Telescope for Large Area Spectroscopy Probe and WFIRST together will produce a 3D map of the Universe over 2 000 deg^2, the definitive data sets for studying galaxy evolution, probing dark matter, dark energy and modifications of General Relativity, and quantifying the 3D structure and stellar content of the Milky Way. Astrophysics Telescope for Large Area Spectroscopy Probe science spans four broad categories: (1) Revolutionising galaxy evolution studies by tracing the relation between galaxies and dark matter from galaxy groups to cosmic voids and filaments, from the epoch of reionisation through the peak era of galaxy assembly; (2) Opening a new window into the dark Universe by weighing the dark matter filaments using 3D weak lensing with spectroscopic redshifts, and obtaining definitive measurements of dark energy and modification of General Relativity using galaxy clustering; (3) Probing the Milky Way’s dust-enshrouded regions, reaching the far side of our Galaxy; and (4) Exploring the formation history of the outer Solar System by characterising Kuiper Belt Objects. Astrophysics Telescope for Large Area Spectroscopy Probe is a 1.5 m telescope with a field of view of 0.4 deg^2, and uses digital micro-mirror devices as slit selectors. It has a spectroscopic resolution of R = 1 000, and a wavelength range of 1–4 μm. The lack of slit spectroscopy from space over a wide field of view is the obvious gap in current and planned future space missions; Astrophysics Telescope for Large Area Spectroscopy fills this big gap with an unprecedented spectroscopic capability based on digital micro-mirror devices (with an estimated spectroscopic multiplex factor greater than 5 000). Astrophysics Telescope for Large Area Spectroscopy is designed to fit within the National Aeronautics and Space Administration probe-class space mission cost envelope; it has a single instrument, a telescope aperture that allows for a lighter launch vehicle, and mature technology (we have identified a path for digital micro-mirror devices to reach Technology Readiness Level 6 within 2 yr). Astrophysics Telescope for Large Area Spectroscopy Probe will lead to transformative science over the entire range of astrophysics: from galaxy evolution to the dark Universe, from Solar System objects to the dusty regions of the Milky Way
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