VINTERGATAN III: how to reset the metallicity of the Milky Way

Using the cosmological zoom simulation VINTERGATAN, we present a new scenario for the onset of star formation at the metal-poor end of the low-[$\alpha$/Fe] sequence in a Milky Way-like galaxy. In this scenario, the galaxy is fueled by two distinct gas flows. One is enriched by outflows from massive galaxies, but not the other. While the former feeds the inner galactic region, the latter fuels an outer gas disk, inclined with respect to the main galactic plane, and with a significantly poorer chemical content. The first passage of the last major merger galaxy triggers tidal compression in the outer disk, which increases the gas density and eventually leads to star formation, at a metallicity 0.75 dex lower than the inner galaxy. This forms the first stars of the low-[$\alpha$/Fe] sequence. These in situ stars have halo-like kinematics, similarly to what is observed in the Milky Way, due to the inclination of the outer disk which eventually aligns with the inner one via gravitational torques. We show that this tilting disk scenario is likely to be common in Milky-Way like galaxies. This process implies that the low-[$\alpha$/Fe] sequence is populated in situ, simultaneously from two formation channels, in the inner and the outer galaxy, with distinct metallicities. This contrasts with purely sequential scenarios for the assembly of the Milky Way disk and could be tested observationally.Comment: MNRAS in press. Movies available at http://www.astro.lu.se/~florent/vintergatan.ph

VINTERGATAN II: the history of the Milky Way told by its mergers

Using the VINTERGATAN cosmological zoom simulation, we explore the contributions of the in situ and accreted material, and the effect of galaxy interactions and mergers in the assembly of a Milky Way-like galaxy. We find that the initial growth phase of galaxy evolution, dominated by repeated major mergers, provides the necessary physical conditions for the assembly of a thick, kinematically hot disk populated by high-[$\alpha$/Fe] stars, formed both in situ and in accreted satellite galaxies. We find that the diversity of evolutionary tracks followed by the simulated galaxy and its progenitors leads to very little overlap of the in situ and accreted populations for any given chemical composition. At a given age, the spread in [$\alpha$/Fe] abundance ratio results from the diversity of physical conditions in VINTERGATAN and its satellites, with an enhancement in [$\alpha$/Fe] found in stars formed during starburst episodes. Later, the cessation of the merger activity promotes the in situ formation of stars in the low-[$\alpha$/Fe] regime, in a radially extended, thin and overall kinematically colder disk, thus establishing chemically bimodal thin and thick disks, in line with observations. We draw links between notable features in the [Fe/H] - [$\alpha$/Fe] plane with their physical causes, and propose a comprehensive formation scenario explaining self-consistently, in the cosmological context, the main observed properties of the Milky Way.Comment: MNRAS in press. Movies available at http://www.astro.lu.se/~florent/vintergatan.ph

VINTERGATAN I: The origins of chemically, kinematically and structurally distinct discs in a simulated Milky Way-mass galaxy

Spectroscopic surveys of the Milky Way's stars have revealed spatial, chemical and kinematical structures that encode its history. In this work, we study their origins using a cosmological zoom simulation, VINTERGATAN, of a Milky Way-mass disc galaxy. We find that in connection to the last major merger at $z\sim 1.5$, cosmological accretion leads to the rapid formation of an outer, metal-poor, low-[$\alpha$/Fe] gas disc around the inner, metal-rich galaxy containing the old high-[$\alpha$/Fe] stars. This event leads to a bimodality in [$\alpha$/Fe] over a range of [Fe/H]. A detailed analysis of how the galaxy evolves since $z\sim 1$ is presented. We demonstrate the way in which inside-out growth shapes the radial surface density and metallicity profile and how radial migration preferentially relocates stars from the inner to the outer disc. Secular disc heating is found to give rise to increasing velocity dispersions and scaleheights with stellar age, which together with disc flaring explains several trends observed in the Milky Way, including shallower radial [Fe/H]-profiles above the midplane. We show how the galaxy formation scenario imprints non-trivial mappings between structural associations (i.e. thick and thin discs), velocity dispersions, $\alpha$-enhancements, and ages of stars, e.g. the most metal-poor stars in the low-[$\alpha$/Fe] sequence are found to have a scaleheight comparable to old high-[$\alpha$/Fe] stars. Finally, we illustrate how at low spatial resolution, comparable to the thickness of the galaxy, the proposed pathway to distinct sequences in [$\alpha$/Fe]-[Fe/H] cannot be captured.Comment: 20 pages, MNRAS submitted, comments welcome. Movies available at http://www.astro.lu.se/~florent/vintergatan.ph

Evaluation of a Command-line Parser-based Order Entry Pathway for the Department of Veterans Affairs Electronic Patient Record

Objective: To improve and simplify electronic order entry in an existing electronic patient record, the authors developed an alternative system for entering orders, which is based on a command- interface using robust and simple natural-language techniques. Design: The authors conducted a randomized evaluation of the new entry pathway, measuring time to complete a standard set of orders, and users' satisfaction measured by questionnaire. A group of 16 physician volunteers from the staff of the Department of Veterans Affairs Puget Sound Health Care System-Seattle Division participated in the evaluation. Results: Thirteen of the 16 physicians (81%) were able to enter medical orders more quickly using the natural-language-based entry system than the standard graphical user interface that uses menus and dialogs (mean time spared, 16.06 ± 4.52 minutes; P=0.029). Compared with the graphical user interface, the command--based pathway was perceived as easier to learn (P<0.01), was considered easier to use and faster (P<0.01), and was rated better overall (P<0.05). Conclusion: Physicians found the command- interface easier to learn and faster to use than the usual menu-driven system. The major advantage of the system is that it combines an intuitive graphical user interface with the power and speed of a natural-language analyze

Vaccination of Rhesus Macaques with a Recombinant Measles Virus Expressing Interleukin-12 Alters Humoral and Cellular Immune Responses

Lack of a vaccine for infants and immunosuppression after infection are problems associated with measles virus (MV). Because interleukin (IL)-12 has been used successfully as a vaccine adjuvant and because inhibition of IL-12 expression has been associated with immunosuppression during measles, the addition of IL-12 may enhance the immune response to MV. To determine the effect of IL-12 supplementation, rhesus macaques were vaccinated with a recombinant MV expressing IL-12; these macaques had increased interferon-γ production by CD4+ T cells, decreased production of IL-4, and lower levels of MV-specific immunoglobulin G4 and neutralizing antibody. Lymphoproliferative responses to mitogen were not improved. IL-12 supplementation altered the T helper type 2 bias of the immune response after MV vaccination, had a detrimental effect on the protective neutralizing antibody response, and did not improve other manifestations of immunosuppression. Reduced IL-12 levels are not the sole factor in MV-induced immunosuppressio

Relationships of Stigma and Shame to Gonorrhea and HIV Screening

Objectives. The purpose of this study was to assess the relationships between stigma and shame associated with seeking treatment for sexually transmitted diseases (STDs) and undergoing testing for gonorrhea and HIV. Methods. Participants were 847 males and 1126 females (mean age: 24.9 years) in 7 cities. Two scales assessed STD-related stigma and STD-related shame. Results. Rates of stigma and shame were higher among participants without a gonorrhea test in the past year and among those without an HIV test. Sex, age, health service use, previous suspicion of gonorrhea, and low levels of stigma were independently associated with gonorrhea testing. Age, enrollment site, use of health services, gonorrhea testing, and low levels of stigma were independently associated with HIV testing. Conclusions. Shame is part of the experience of seeking STD-related care, but stigma may be a more powerful barrier to obtaining such care

Using the Stages of Change Model to Choose an Optimal Health Marketing Target

Background: In the transtheoretical model of behavior change, “stages of change” are defined as Precontemplation (not even thinking about changing), Contemplation, Preparation, Action, and Maintenance (maintaining the behavior change). Marketing principles suggest that efforts should be targeted at persons most likely to “buy the product.” Objectives: To examine the effect of intervening at different stages in populations of smokers, with various numbers of people in each “stage of change.” One type of intervention would increase by 10% the probability of a person moving to the next higher stage of change, such as from Precontemplation to Contemplation. The second type would decrease by 10% the probability of relapsing to the next lower stage, such as from Maintenance to Action, and also of changing from Never Smoker to Smoker. Nine hypothetical interventions were compared with the status quo, to determine which type of intervention would provide the most improvement in population smoking. Methods: Three datasets were used to estimate the probability of moving among the stages of change for smoking. Those probabilities were used to create multi-state life tables, which yielded estimates of the expected number of years the population would spend in each stage of change starting at age 40. We estimated the effect of each hypothetical intervention, and compared the intervention effects. Several initial conditions, time horizons, and criteria for success were examined. Results: A population of 40-year-olds in Precontemplation had a further life expectancy of 36 years, of which 26 would be spent in the Maintenance stage. In a population of former and current smokers, moving more persons from the Action to the Maintenance stage (a form of relapse prevention) decreased the number of years spent smoking more than the any other intervention. In a population of 40-year-olds that included Never Smokers, primary smoking prevention was the most effective. The results varied somewhat by the choice of criterion, the length of follow-up, the initial stage distribution, the data, and the sensitivity analyses. Conclusions: In a population of 40-year-olds, smokers were likely to achieve Maintenance without an intervention. On the population basis, targeting quitters and never-smokers was more effective than targeting current smokers. This finding is supported by some principles of health marketing. Additional research should target younger ages as well as other health behaviors