The Stellar Metallicity Distribution Function of the Galactic Halo from SDSS Photometry

We explore the stellar metallicity distribution function of the Galactic halo based on SDSS ugriz photometry. A set of stellar isochrones is calibrated using observations of several star clusters and validated by comparisons with medium-resolution spectroscopic values over a wide range of metal abundance. We estimate distances and metallicities for individual main-sequence stars in the multiply scanned SDSS Stripe 82, at heliocentric distances in the range 5 - 8 kpc and |b| > 35 deg, and find that the in situ photometric metallicity distribution has a shape that matches that of the kinematically-selected local halo stars from Ryan & Norris. We also examine independent kinematic information from proper-motion measurements for high Galactic latitude stars in our sample. We find that stars with retrograde rotation in the rest frame of the Galaxy are generally more metal poor than those exhibiting prograde rotation, which is consistent with earlier arguments by Carollo et al. that the halo system comprises at least two spatially overlapping components with differing metallicity, kinematics, and spatial distributions. The observed photometric metallicity distribution and that of Ryan & Norris can be described by a simple chemical evolution model by Hartwick (or by a single Gaussian distribution); however, the suggestive metallicity-kinematic correlation contradicts the basic assumption in this model that the Milky Way halo consists primarily of a single stellar population. When the observed metallicity distribution is deconvolved using two Gaussian components with peaks at [Fe/H] ~ -1.7 and -2.3, the metal-poor component accounts for ~20% - 35% of the entire halo population in this distance range.Comment: Accepted for publication in Ap

A Photometric Metallicity Estimate of the Virgo Stellar Overdensity

We determine photometric metal abundance estimates for individual main-sequence stars in the Virgo Overdensity (VOD), which covers almost 1000 deg^2 on the sky, based on a calibration of the metallicity sensitivity of stellar isochrones in the gri filter passbands using field stars with well-determined spectroscopic metal abundances. Despite the low precision of the method for individual stars, we derive [Fe/H] = -2.0 +/-0.1 (internal) +/-0.5 (systematic) for the metal abundance of the VOD from photometric measurements of 0.7 million stars in the Northern Galactic hemisphere with heliocentric distances from ~10 kpc to ~20 kpc. The metallicity of the VOD is indistinguishable, within Delta [Fe/H] < 0.2, from that of field halo stars covering the same distance range. This initial application suggests that the SDSS gri passbands can be used to probe the properties of main-sequence stars beyond ~10 kpc, complementing studies of nearby stars from more metallicity-sensitive color indices that involve the u passband.Comment: 5 pages, 3 figures, Accepted for publication in ApJ Letter

Metallicity Mapping with gri Photometry: The Virgo Overdensity and the Halos of the Galaxy

We describe the methodology required for estimation of photometric estimates of metallicity based on the SDSS gri passbands, which can be used to probe the properties of main-sequence stars beyond ~ 10 kpc, complementing studies of nearby stars from more metallicity-sensitive color indices that involve the u passband. As a first application of this approach, we determine photometric metal abundance estimates for individual main-sequence stars in the Virgo Overdensity, which covers almost 1000 square degrees on the sky, based on a calibration of the metallicity sensitivity of stellar isochrones in the gri filter passbands using field stars with well-determined spectroscopic metal abundances. Despite the low precision of the method for individual stars, internal errors of in [Fe/H] ~ +/- 0.1 dex can be achieved for bulk stellar populations. The global metal abundance of the Virgo Overdensity determined in this way is = -2.0 +/- 0.1 (internal) +/- 0.5 (systematic), from photometric measurements of 0.7 million stars with heliocentric distances from ~ 10 kpc to ~ 20 kpc. A preliminary metallicity map, based on results for 2.9 million stars in the northern SDSS DR-7 footprint, exhibits a shift to lower metallicities as one proceeds from the inner- to the outer-halo population, consistent with recent interpretation of the kinematics of local samples of stars with spectroscopically available metallicity estimates and full space motions.Comment: 4 pages, 2 figures, to appear in IAU Symp. 26

Preliminary Findings on Processes of Change and Moderators for Cognitive Defusion and Restructuring Delivered Through Mobile Apps

A process-based therapy approach emphasizes examining how and for whom specific therapeutic components linked to specific processes of change function. This preliminary study explored the processes of change for cognitive defusion and restructuring with daily ratings of self-criticism from a larger component trial as well as self-compassion as a moderator of these daily effects. A sample of 51 adults high in self-criticism (M age = 22.69, 78% female, 88% non-Hispanic White) were randomized to a cognitive defusion or restructuring mobile app for two weeks and completed daily assessments. Both conditions improved over time on daily frequency, defused noticing, challenging, and believability of self-critical thoughts as well as valued actions, with larger improvements in the defusion condition only for thought frequency and defused noticing. Global self-compassion moderated several effects such that only participants lower in self-compassion improved over time on daily self-criticism processes in the restructuring condition, while effects over time in the defusion condition generally did not vary by level of self-compassion. Improvements in daily frequency, defused noticing, and challenging self-critical thoughts as well as valued action each predicted global improvements in self-criticism at post-intervention across conditions. Overall, these preliminary results suggest cognitive defusion and restructuring may have some similar effects on self-criticism related processes of change, particularly for those low in self-compassion. However, defusion may produce larger effects on some targeted processes, especially among those with higher self-compassion

Modeling Anti-HIV-1 HSPC-Based Gene Therapy in Humanized Mice Previously Infected with HIV-1.

Investigations of anti-HIV-1 human hematopoietic stem/progenitor cell (HSPC)-based gene therapy have been performed by HIV-1 challenge after the engraftment of gene-modified HSPCs in humanized mouse models. However, the clinical application of gene therapy is to treat HIV-1-infected patients. Here, we developed a new method to investigate an anti-HIV-1 HSPC-based gene therapy in humanized mice previously infected with HIV-1. First, humanized mice were infected with HIV-1. When plasma viremia reached &gt;107 copies/mL 3&nbsp;weeks after HIV-1 infection, the mice were myeloablated with busulfan and transplanted with anti-HIV-1 gene-modified CD34+ HSPCs transduced with a lentiviral vector expressing two short hairpin RNAs (shRNAs) against CCR5 and HIV-1 long terminal repeat (LTR), along with human thymus tissue under the kidney capsule. Anti-HIV-1 vector-modified human CD34+ HSPCs successfully repopulated peripheral blood and lymphoid tissues in HIV-1 previously infected humanized mice. Anti-HIV-1 shRNA vector-modified CD4+ T lymphocytes showed selective advantage in HIV-1 previously infected humanized mice. This new method will be useful for investigations of anti-HIV-1 gene therapy when testing in a more clinically relevant experimental setting

Formation and Evolution of the Disk System of the Milky Way: [alpha/Fe] Ratios and Kinematics of the SEGUE G-Dwarf Sample

We employ measurements of the [alpha/Fe] ratio derived from low-resolution (R~2000) spectra of 17,277 G-type dwarfs from the SEGUE survey to separate them into likely thin- and thick-disk subsamples. Both subsamples exhibit strong gradients of orbital rotational velocity with metallicity, of opposite signs, -20 to -30 km/s/dex for the thin-disk and +40 to +50 km/s/dex for the thick-disk population. The rotational velocity is uncorrelated with Galactocentric distance for the thin-disk subsample, and exhibits a small trend for the thick-disk subsample. The rotational velocity decreases with distance from the plane for both disk components, with similar slopes (-9.0 {\pm} 1.0 km/s/kpc). Thick-disk stars exhibit a strong trend of orbital eccentricity with metallicity (about -0.2/dex), while the eccentricity does not change with metallicity for the thin-disk subsample. The eccentricity is almost independent of Galactocentric radius for the thin-disk population, while a marginal gradient of the eccentricity with radius exists for the thick-disk population. Both subsamples possess similar positive gradients of eccentricity with distance from the Galactic plane. The shapes of the eccentricity distributions for the thin- and thick-disk populations are independent of distance from the plane, and include no significant numbers of stars with eccentricity above 0.6. Among several contemporary models of disk evolution we consider, radial migration appears to have played an important role in the evolution of the thin-disk population, but possibly less so for the thick disk, relative to the gas-rich merger or disk heating scenarios. We emphasize that more physically realistic models and simulations need to be constructed in order to carry out the detailed quantitative comparisons that our new data enable.Comment: Accepted for publication in ApJ, 18 pages, 12 figures, 2 tables, emulateapj forma

Guidelines for randomized clinical trial protocol content: a systematic review

BACKGROUND: All randomized clinical trials (RCTs) require a protocol; however, numerous studies have highlighted protocol deficiencies. Reporting guidelines may improve the content of research reports and, if developed using robust methods, may increase the utility of reports to stakeholders. The objective of this study was to systematically identify and review RCT protocol guidelines, to assess their characteristics and methods of development, and to compare recommendations. METHODS: We conducted a systematic review of indexed literature (MEDLINE, EMBASE and the Cochrane Methodology Register from inception to September 2010; reference lists; related article features; forward citation searching) and a targeted search of supplementary sources, including a survey of major trial funding agencies in six countries. Records were eligible if they described a content guideline in English or French relevant to RCT protocols. Guidelines were excluded if they specified content for protocols for trials of specific procedures or conditions or were intended to assess trial quality. We extracted guideline characteristics and methods. Content was mapped for a subset of guidelines that described development methods or had institutional endorsement. RESULTS: Forty guidelines published in journals, books and institutional reports were included in the review; seven were specific to RCT protocols. Only eight (20%) described development methods which included informal consensus methods, pilot testing and formal validation; no guideline described all of these methods. No guideline described formal consensus methods or a systematic retrieval of empirical evidence to inform its development. The guidelines included a median of 23 concepts per guideline (interquartile range (IQR) = 14 to 34; range = 7 to 109). Among the subset of guidelines (n = 23) for which content was mapped, approximately 380 concepts were explicitly addressed (median concepts per guideline IQR = 31 (24,80); range = 16 to 150); most concepts were addressed in a minority of guidelines. CONCLUSIONS: Existing guidelines for RCT protocol content varied substantially in their recommendations. Few reports described the methods of guideline development, limiting comparisons of guideline validity. Given the importance of protocols to diverse stakeholders, we believe a systematically developed, evidence-informed guideline for clinical trial protocols is needed

Spectroscopic Survey of G and K Dwarfs in the Hipparcos Catalog. I. Comparison between the Hipparcos and Photometric Parallaxes

The tension between the Hipparcos parallax of the Pleiades and other independent distance estimates continues even after the new reduction of the Hipparcos astrometric data and the development of a new geometric distance measurement for the cluster. A short Pleiades distance from the Hipparcos parallax predicts a number of stars in the solar neighborhood that are sub-luminous at a given photospheric abundance. We test this hypothesis using the spectroscopic abundances for a subset of stars in the Hipparcos catalog, which occupy the same region as the Pleiades in the color–magnitude diagram. We derive stellar parameters for 170 nearby G- and K-type field dwarfs in the Hipparcos catalog based on high-resolution spectra obtained using KPNO 4 m echelle spectrograph. Our analysis shows that, when the Hipparcos parallaxes are adopted, most of our sample stars follow empirical color–magnitude relations. A small fraction of stars are too faint compared to main-sequence fitting relations by ΔM_V ≳ 0.3 mag, but the differences are marginal at a 2σ level, partly due to relatively large parallax errors. On the other hand, we find that the photometric distances of stars showing signatures of youth as determined from lithium absorption line strengths and R_(HK)^' chromospheric activity indices are consistent with the Hipparcos parallaxes. Our result is contradictory to a suggestion that the Pleiades distance from main-sequence fitting is significantly altered by stellar activity and/or the young age of its stars, and provides an additional supporting evidence for the long-distance scale of the Pleiades

The SEGUE Stellar Parameter Pipeline. IV. Validation with an Extended Sample of Galactic Globular and Open Clusters

Spectroscopic and photometric data for likely member stars of five Galactic globular clusters (M3, M53, M71, M92, and NGC 5053) and three open clusters (M35, NGC 2158, and NGC 6791) are processed by the current version of the SEGUE Stellar Parameter Pipeline (SSPP), in order to determine estimates of metallicities and radial velocities for the clusters. These results are then compared to values from the literature. We find that the mean metallicity () and mean radial velocity () estimates for each cluster are almost all within 2{\sigma} of the adopted literature values; most are within 1{\sigma}. We also demonstrate that the new version of the SSPP achieves small, but noteworthy, improvements in estimates at the extrema of the cluster metallicity range, as compared to a previous version of the pipeline software. These results provide additional confidence in the application of the SSPP for studies of the abundances and kinematics of stellar populations in the Galaxy.Comment: 98 pages, 31 figures; accepted for publication in A