36 research outputs found

    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

    Seeding Science, Courting Conclusions: Reexamining the Intersection of Science, Corporate Cash, and the Law

    Full text link
    Social scientists have expressed strong views on corporate influences over science, but most attention has been devoted to broad, Black/White arguments, rather than to actual mechanisms of influence. This paper summarizes an experience where involvement in a lawsuit led to the discovery of an unexpected mechanism: A large corporation facing a multibillion-dollar court judgment quietly provided generous funding to well-known scientists (including at least one Nobel prize winner) who would submit articles to "open," peer-reviewed journals, so that their "unbiased science" could be cited in an appeal to the Supreme Court. On balance, the corporation's most effective techniques of influence may have been provided not by overt pressure, but by encouraging scientists to continue thinking of themselves as independent and impartial

    Quality of generic medicines in South Africa: Perceptions versus Reality – A qualitative study

    Get PDF
    <p>Abstract</p> <p>Background</p> <p>Generic Medicines are an important policy option allowing for access to affordable, essential medicines. Quality of generic medicines must be guaranteed through the activities of national medicines regulatory authorities. Existing negative perceptions surrounding the quality of generic medicines must be addressed to ensure that people use them with confidence. Campaigns to increase the uptake of generic medicines by consumers and providers of healthcare need to be informed by local norms and practices. This study sought to compare South African consumers’ and healthcare providers’ perceptions of quality of generics to the actual quality of selected products.</p> <p>Methods</p> <p>The study was conducted at the local level in three cities of South Africa: Johannesburg, Durban and Cape Town. Purposive sampling was used to recruit consumer participants (n = 73) and random sampling used to recruit healthcare providers from public and private sectors (n = 15). Data were obtained through twelve focus group discussions with consumers and semi-structured interviews (n = 15) with healthcare providers in order to gain familiarity with perceptions of quality. One hundred and thirty five products comprising paracetamol tablets (n = 47), amoxicillin capsules (n = 45) and hydrochlorothiazide tablets (n = 43) were sourced from public and private sector healthcare providers. These products were subjected to <it>in vitro</it> dissolution, uniformity of weight and identity (Fourier Transformed Infrared Spectroscopy) tests using prescribed methods from the British (2005) and United States Pharmacopeias (2006).</p> <p>Results</p> <p>Respondents described drug quality in relation to the effect on symptoms. Procurement and use behavior of healthcare providers was influenced by prior experience, manufacturers’ names and consumers’ ability to pay. All formulations passed the <it>in vitro</it> tests for quality.</p> <p>Conclusions</p> <p>This study showed clear differences between perceptions of quality and actual quality of medicines suggesting deficiencies in public engagement by government regarding the implementation of generic medicines policy. Implementation of generic medicines policy requires the involvement of consumers and healthcare providers to specifically address their information gaps and needs.</p
    corecore