156 research outputs found

    The Overdensity in Virgo, Sagittarius Debris, and the Asymmetric Spheroid

    Full text link
    We investigate the relationship between several previously identified Galactic halo stellar structures in the direction of Virgo using imaging and spectroscopic observations of F turnoff stars and blue horizontal branch stars from the Sloan Digital Sky Survey (SDSS) and the Sloan Extension for Galactic Understanding and Exploration (SEGUE). We show that the Sagittarius dwarf leading tidal tail does not pass through the solar neighborhood; it misses the Sun by more than 15 kpc, passing through the Galactic plane outside the Solar Circle. It also is not spatially coincident with the large stellar overdensity S297+63-20.5 in the Virgo constellation. S297+63-20.5 has a distinct turnoff color and kinematics. Faint (g ~ 20.3) turnoff stars in S297+63-20.5 have line-of-sight, Galactic standard of rest velocities V(GSR)= 130 +/- 10 km/s, opposite in sign to infalling Sgr tail stars. The path of the Sgr leading tidal tail is also inconsistent with the positions of some of the nearer stars with which it has been associated, and whose velocities have favored models with prolate Milky Way potentials. We additionally show that the number densities of brighter (g ~ 19.8) F turnoff stars are not symmetric about the Galactic center, and that this discrepancy is not primarily due to the S297+63-20.5 moving group. Either the spheroid is asymmetric about the Galactic center, or there are additional substructures that conspire to be on the same side of the Galaxy as S297+63-20.5. The S297+63-20.5 overdensity in Virgo is likely associated with two other previously identified Virgo substructures: the Virgo Stellar Stream (VSS) and the Virgo Overdensity (VOD). However, the velocity difference between the VSS and S297+63-20.5 and the difference in distance estimates between the VOD and S297+63-20.5 must be reconciled.Comment: 10 figures, ApJ in pres

    Markov Random Field Segmentation of Brain MR Images

    Full text link
    We describe a fully-automatic 3D-segmentation technique for brain MR images. Using Markov random fields the segmentation algorithm captures three important MR features, i.e. non-parametric distributions of tissue intensities, neighborhood correlations and signal inhomogeneities. Detailed simulations and real MR images demonstrate the performance of the segmentation algorithm. The impact of noise, inhomogeneity, smoothing and structure thickness is analyzed quantitatively. Even single echo MR images are well classified into gray matter, white matter, cerebrospinal fluid, scalp-bone and background. A simulated annealing and an iterated conditional modes implementation are presented. Keywords: Magnetic Resonance Imaging, Segmentation, Markov Random FieldsComment: 34 pages, 10 figures; the paper (published in 1997) has introduced the concept of Markov random field to the segmentation of medical MR images. For the published version see http://dx.doi.org/10.1109/42.65088

    SPENDING AND SAVING HABITS OF UNIVERSITY STUDENTS

    Get PDF
    The spending behavior of college students combined with their limited understanding of money management promotes habits that may lead to costly financial mistakes in the future. The quantitative survey was conducted to determine  the spending and saving habits of randomly selected students from the college of business. These students were enrolled in Accountancy, Business Administration, and Office Administration programs in which majority (55%) are females. Of the 90 respondents, 76% received an allowance from their parents, 16% from their sponsors and 6% have part-time jobs, 2% have personal investments  where they get their allowances. Included in the survey questionnaire were their expenditures  from monthly allowances which include the following: 1) food, 2) travel, 3) clothing/accessories, 4) electronics gadgets, 4) groceries, 5) beauty products and services, 6) school supplies, 7) cellphone load, 8)  books and magazines. Results show that the top five priorities where students from the college of business spent their monthly allowance were clothing/accessories (41.1%), school supplies (37.8%), books (36.7%), beauty products (32.2%), and beauty services (27.8%). Students spending habits were identified. Peer pressure and quality of the products were some contributing factors in the buying decision of the students.  The majority (82.2%) of the students saved money from their monthly allowance. This study emphasized the need for financial literacy awareness among the students particularly in the college of business so they will learn to practice the correct skill in money management

    SDSSJ103913.70+533029.7: A Super Star Cluster in the Outskirts of a Galaxy Merger

    Full text link
    We describe the serendipitous discovery in the spectroscopic data of the Sloan Digital Sky Survey of a star-like object, SDSSJ103913.70+533029.7, at a heliocentric radial velocity of +1012 km/s. Its proximity in position and velocity to the spiral galaxy NGC 3310 suggests an association with the galaxy. At this distance, SDSSJ103913.70+533029.7 has the luminosity of a super star cluster and a projected distance of 17 kpc from NGC 3310. Its spectroscopic and photometric properties imply a mass of > 10^6 solar masses and an age close to that of the tidal shells seen around NGC 3310, suggesting that it formed in the event which formed the shells.Comment: Accepted by AJ: 4 figures (1 color

    The Milky Way Tomography With SDSS. III. Stellar Kinematics

    Get PDF
    We study Milky Way kinematics using a sample of 18.8 million main-sequence stars with r 20 degrees). We find that in the region defined by 1 kpc < Z < 5 kpc and 3 kpc < R < 13 kpc, the rotational velocity for disk stars smoothly decreases, and all three components of the velocity dispersion increase, with distance from the Galactic plane. In contrast, the velocity ellipsoid for halo stars is aligned with a spherical coordinate system and appears to be spatially invariant within the probed volume. The velocity distribution of nearby (Z < 1 kpc) K/M stars is complex, and cannot be described by a standard Schwarzschild ellipsoid. For stars in a distance-limited subsample of stars (< 100 pc), we detect a multi-modal velocity distribution consistent with that seen by HIPPARCOS. This strong non-Gaussianity significantly affects the measurements of the velocity-ellipsoid tilt and vertex deviation when using the Schwarzschild approximation. We develop and test a simple descriptive model for the overall kinematic behavior that captures these features over most of the probed volume, and can be used to search for substructure in kinematic and metallicity space. We use this model to predict further improvements in kinematic mapping of the Galaxy expected from Gaia and the Large Synoptic Survey Telescope.NSF AST-615991, AST-0707901, AST-0551161, AST-02-38683, AST-06-07634, AST-0807444, PHY05-51164NASA NAG5-13057, NAG5-13147, NNXO-8AH83GPhysics Frontier Center/Joint Institute for Nuclear Astrophysics (JINA) PHY 08-22648U.S. National Science FoundationMarie Curie Research Training Network ELSA (European Leadership in Space Astrometry) MRTN-CT-2006-033481Fermi Research Alliance, LLC, United States Department of Energy DE-AC02-07CH11359Alfred P. Sloan FoundationParticipating InstitutionsJapanese MonbukagakushoMax Planck SocietyHigher Education Funding Council for EnglandMcDonald Observator

    The Milky Way Tomography with SDSS: III. Stellar Kinematics

    Full text link
    We study Milky Way kinematics using a sample of 18.8 million main-sequence stars with r<20 and proper-motion measurements derived from SDSS and POSS astrometry, including ~170,000 stars with radial-velocity measurements from the SDSS spectroscopic survey. Distances to stars are determined using a photometric parallax relation, covering a distance range from ~100 pc to 10 kpc over a quarter of the sky at high Galactic latitudes (|b|>20 degrees). We find that in the region defined by 1 kpc <Z< 5 kpc and 3 kpc <R< 13 kpc, the rotational velocity for disk stars smoothly decreases, and all three components of the velocity dispersion increase, with distance from the Galactic plane. In contrast, the velocity ellipsoid for halo stars is aligned with a spherical coordinate system and appears to be spatially invariant within the probed volume. The velocity distribution of nearby (Z<1Z<1 kpc) K/M stars is complex, and cannot be described by a standard Schwarzschild ellipsoid. For stars in a distance-limited subsample of stars (<100 pc), we detect a multimodal velocity distribution consistent with that seen by HIPPARCOS. This strong non-Gaussianity significantly affects the measurements of the velocity ellipsoid tilt and vertex deviation when using the Schwarzschild approximation. We develop and test a simple descriptive model for the overall kinematic behavior that captures these features over most of the probed volume, and can be used to search for substructure in kinematic and metallicity space. We use this model to predict further improvements in kinematic mapping of the Galaxy expected from Gaia and LSST.Comment: 90 pages, 26 figures, submitted to Ap

    Software Engineering for Self-Adaptive Systems: A second Research Roadmap

    Get PDF
    The goal of this roadmap paper is to summarize the state of-the-art and identify research challenges when developing, deploying and managing self-adaptive software systems. Instead of dealing with a wide range of topics associated with the field, we focus on four essential topics of self-adaptation: design space for adaptive solutions, processes, from centralized to decentralized control, and practical run-time verification and validation. For each topic, we present an overview, suggest future directions, and focus on selected challenges. This paper complements and extends a previous roadmap on software engineering for self-adaptive systems published in 2009 covering a different set of topics, and reflecting in part on the previous paper. This roadmap is one of the many results of the Dagstuhl Seminar 10431 on Software Engineering for Self-Adaptive Systems, which took place in October 2010

    The pathophysiology of fluid and electrolyte balance in the older adult surgical patient

    Get PDF
    Background & aims: Age-related physiological changes predispose even the healthy older adult to fluid and electrolyte abnormalities which can cause morbidity and mortality. The aim of this narrative review is to highlight key aspects of age-related pathophysiological changes that affect fluid and electrolyte balance in older adults and underpin their importance in the perioperative period. Methods: The Web of Science, MEDLINE, PubMed and Google Scholar databases were searched using key terms for relevant studies published in English on fluid balance in older adults during the 15 years preceding June 2013. Randomised controlled trials and large cohort studies were sought; other studieswere used when these were not available. The bibliographies of extracted papers were also searched for relevant articles. Results: Older adults are susceptible to dehydration and electrolyte abnormalities, with causes ranging from physical disability restricting access to fluid intake to iatrogenic causes including polypharmacy and unmonitored diuretic usage. Renal senescence, as well as physical and mental decline, increase this susceptibility. Older adults are also predisposed to water retention and related electrolyte abnormalities, exacerbated at times of physiological stress. Positive fluid balance has been shown to be an independent risk factor for morbidity and mortality in critically ill patients with acute kidney injury. Conclusions: Age-related pathophysiological changes in the handling of fluid and electrolytes make older adults undergoing surgery a high-risk group and an understanding of these changes will enable better management of fluid and electrolyte therapy in the older adult

    Thrive: Success Strategies for the Modern-Day Faculty Member

    Get PDF
    The THRIVE collection is intended to help faculty thrive in their roles as educators, scholars, researchers, and clinicians. Each section contains a variety of thought-provoking topics that are designed to be easily digested, guide personal reflection, and put into action. Please use the THRIVE collection to help: Individuals study topics on their own, whenever and wherever they want Peer-mentoring or other learning communities study topics in small groups Leaders and planners strategically insert faculty development into existing meetings Faculty identify campus experts for additional learning, grand rounds, etc. If you have questions or want additional information on a topic, simply contact the article author or email [email protected]://digitalcommons.unmc.edu/facdev_books/1000/thumbnail.jp
    • …
    corecore