6,509 research outputs found

    CNONa and 12C/13C in giants of 10 open clusters

    Full text link
    Evolved low-mass stars of a wide range of metallicity bear signatures of a non-standard mixing event in their surface abundances of Li, C, and N, and in their 12C/13C ratio. A Na overabundance has also been reported in some giants of open clusters but remains controversial. The cause of the extra-mixing has been attributed to thermohaline convection that should take place after the RGB bump for low-mass stars and on the early-AGB for more massive objects. To track the occurrence of this process over a wide mass range, we derive in a homogeneous way the abundances of C, N, O, and Na, as well as the 12C/13C ratio in a sample of 31 giants of 10 open clusters with turn-off masses from 1.7 to 3.1 Msun. A group of first ascent red giants with M/Msun \leq 2.5 exhibits lower [N/C] ratios than those measured in clump giants of the same mass range, suggesting an additional increase in the [N/C] ratio after the first dredge-up. The sodium abundances corrected from NLTE are found to be about solar. [Na/Fe] shows a slight increase of 0.10 dex as a function of stellar mass in the 1.8 to 3.2 Msun range covered by our sample, in agreement with standard first dredge-up predictions. Our results do not support previous claims of sodium overabundances as high as +0.60 dex. An anti-correlation between 12C/13C and turn-off mass is identified and interpreted as being caused by a post-bump thermohaline mixing. Moreover, we find low 12C/13C ratios in a few intermediate-mass early-AGB stars, confirming that an extra-mixing process also operates in stars that do not experienced the RGB bump. In this case, the extra-mixing possibly acts on the early-AGB, in agreement with theoretical expectations for thermohaline mixing. [abridged]Comment: A&A accepted, revised versio

    A comparative study of multiple imputation and subset correspondence analysis in dealing with missing data

    Get PDF
    Methods: Multiple imputation and subset correspondence analysis are applied to a set of child asthma data that is mainly categorical and suffers from non-response. Differences in the methods and in the outcomes they produce are studied. In addition, the inclusion of interactions in a subset correspondence analysis is illustrated. Results: Despite the vast differences in the two approaches, they yielded similar results in the identification of genetic, environmental and socio-economic factors that affect childhood asthma. A number of exposure related variables were found to be associated with the greater severity of asthma. It was also found that a finer distinction between the asthma severity levels and their associations with factors was possible with a subset correspondence analysis, compared to the multiple imputation approach. Conclusions: Both multiple imputation and subset correspondence analysis were able to identify several factors associated with childhood asthma while at the same time successfully managing the missing data. This offers the researcher a choice to select the method that best suits his/her study

    Definitive spectroscopic determination of the transverse interactions responsible for the magnetic quantum tunneling in Mn12-acetate

    Full text link
    We present detailed angle-dependent single crystal electron paramagnetic resonance (EPR) data for field rotations in the hard plane of the S=10 single molecule magnet Mn12-acetate. A clear four-fold variation in the resonance positions may be attributed to an intrinsic fourth order transverse anisotropy (O44). Meanwhile, a four-fold variation of the EPR lineshapes confirms a recently proposed model wherein disorder associated with the acetic acid of crystallization induces a locally varying quadratic (rhombic) transverse anisotropy (O22). These findings explain most aspects of the magnetic quantum tunneling observed in Mn12-acetate.Comment: 7 pages, including figures, accepted for publication in Phys. Rev. Let

    KOI-3890: A high mass-ratio asteroseismic red-giant++M-dwarf eclipsing binary undergoing heartbeat tidal interactions

    Get PDF
    KOI-3890 is a highly eccentric, 153-day period eclipsing, single-lined spectroscopic binary system containing a red-giant star showing solar-like oscillations alongside tidal interactions. The combination of transit photometry, radial velocity observations, and asteroseismology have enabled the detailed characterisation of both the red-giant primary and the M-dwarf companion, along with the tidal interaction and the geometry of the system. The stellar parameters of the red-giant primary are determined through the use of asteroseismology and grid-based modelling to give a mass and radius of M⋆=1.04±0.06  M⊙M_{\star}=1.04\pm0.06\;\textrm{M}_{\odot} and R⋆=5.8±0.2  R⊙R_{\star}=5.8\pm0.2\;\textrm{R}_{\odot} respectively. When combined with transit photometry the M-dwarf companion is found to have a mass and radius of Mc=0.23±0.01  M⊙M_{\mathrm{c}}=0.23\pm0.01\;\textrm{M}_{\odot} and Rc=0.256±0.007  R⊙R_{\mathrm{c}}=0.256\pm0.007\;\textrm{R}_{\odot}. Moreover, through asteroseismology we constrain the age of the system through the red-giant primary to be 9.1−1.7+2.4  Gyr9.1^{+2.4}_{-1.7}\;\mathrm{Gyr}. This provides a constraint on the age of the M-dwarf secondary, which is difficult to do for other M-dwarf binary systems. In addition, the asteroseismic analysis yields an estimate of the inclination angle of the rotation axis of the red-giant star of i=87.6−1.2+2.4i=87.6^{+2.4}_{-1.2} degrees. The obliquity of the system\textemdash the angle between the stellar rotation axis and the angle normal to the orbital plane\textemdash is also derived to give ψ=4.2−4.2+2.1\psi=4.2^{+2.1}_{-4.2} degrees showing that the system is consistent with alignment. We observe no radius inflation in the M-dwarf companion when compared to current low-mass stellar models.Comment: 11 pages, 5 figures, accepted for publication in MNRA

    Correcting the extended-source calibration for the <i>Herschel</i>-SPIRE Fourier-transform spectrometer

    Get PDF
    We describe an update to the Herschel-Spectral and Photometric Imaging Receiver (SPIRE) Fourier-transform spectrometer (FTS) calibration for extended sources, which incorporates a correction for the frequency-dependent far-field feedhorn efficiency, ηff. This significant correction affects all FTS extended-source calibrated spectra in sparse or mapping mode, regardless of the spectral resolution. Line fluxes and continuum levels are underestimated by factors of 1.3–2 in thespectrometer long wavelength band (447–1018 GHz; 671–294 ÎŒm) and 1.4–1.5 in the spectrometer short wavelength band (944–1568 GHz; 318–191 ÎŒm). The correction was implemented in the FTS pipeline version 14.1 and has also been described in the SPIRE Handbook since 2017 February. Studies based on extended-source calibrated spectra produced prior to this pipeline version should be critically reconsidered using the current products available in the Herschel Science Archive. Once the extended-source calibrated spectra are corrected for ηff, the synthetic photometry and the broad-band intensities from SPIRE photometer maps agree within 2–4 per cent – similar levels to the comparison of point-source calibrated spectra and photometry from point-source calibrated maps. The two calibration schemes for the FTS are now self-consistent: the conversion between the corrected extended-source and point-source calibrated spectra can be achieved with the beam solid angle and a gain correction that accounts for the diffraction loss

    Assessing gender mainstreaming in the education sector: depoliticised technique or a step towards women's rights and gender equality?

    Get PDF
    In 1995 the Beijing Conference on Women identified gender mainstreaming as a key area for action. Policies to effect gender mainstreaming have since been widely adopted. This special issue of Compare looks at research on how gender mainstreaming has been used in government education departments, schools, higher education institutions, international agencies and NGOs .1 In this introduction we first provide a brief history of the emergence of gender mainstreaming and review changing definitions of the term. In the process we outline some policy initiatives that have attempted to mainstream gender and consider some difficulties with putting ideas into practice, particularly the tensions between a technical and transformative interpretations . Much of the literature about experiences with gender mainstreaming tends to look at organizational processes and not any specificities of a particular social sector. However, in our second section, we are concerned to explore whether institutional forms and particular actions associated with education give gender mainstreaming in education sites some distinctive features. In our last section we consider some of the debates about global and local negotiations in discussions of gender policy and education and the light this throws on gender mainstreaming. In so doing, we place the articles that follow in relation to contestations over ownership, political economy, the form and content of education practice and the social complexity of gender equality

    Physiological risk profiles and allostatic load: Using latent profile analysis to examine socioeconomic differences in physiological patterns of risk

    Get PDF
    Purpose. The current study sought to expand implications of physiological weathering through the application of latent profile analysis to stress biomarkers to address limitations of traditional allostatic load calculations. Methods. Latent profile analysis was applied biomarkers used in traditional allostatic load metrics to identify physiological risk profiles in the 2007-20010 National Health and Nutritional and Examination Survey. Multinomial logistic regression was used to determine the probability of risk profiles by race/ethnicity, age, gender, and poverty income ratio (PIR). Mean allostatic load score was assessed across each risk profile. Results. Latent profile analysis identified four distinct profiles labeled low risk, inflammatory risk, cardiovascular risk, and hypertension risk. Race, age, and gender significantly increased odds of exhibiting a risk profile. Compared to Whites, Hispanics had significant higher odds of inflammatory (OR=1.43, 95% CI [1.06-1.92]) and cardiovascular risk profiles (OR=1.63, 95% CI [1.09-2.43]) while Blacks had higher odds of inflammatory (OR=1.76 95% CI [1.25-2.47]), cardiovascular (OR=2.12, 95% CI, [1.39-3.27]) and hypertension risk profiles (OR= 1.78, 95% CI [1.21-2.59]). Females held significant greater odds of all risk categories except hypertension in which they held the lowest odds (OR= .19, 95% CI [.14-.25]). Mean allostatic load scores were highest in the inflammatory (M=3.99, SD=1.66) and cardiovascular risk profiles (M=4.4, SD=1.84). Conclusions. Employing latent profile analysis may expand traditional allostatic load methodology by identifying physiological risk patterns among those who experience allostatic load early in life. This may be useful for examining how cultural specific interventions may reduce cardiovascular risk among those exhibiting physiological risk profiles
    • 

    corecore