232 research outputs found

    The ages of stars: The horizontal branch

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    Gender Differences in the Effect of Residential Segregation on Workplace Segregation among Newly Arrived Immigrants

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    Contemporary cities are becoming more and more diverse in population as a result of immigration. Research also shows that within cities residential neighborhoods are becoming ethnically more diverse, but that residential segregation has remained persistently high. High levels of segregation are often seen as negative, preventing integration of immigrants in their host society and having a negative impact on people's lives. Segregation research often focuses on residential neighborhoods, but ignores the fact that a lot of interaction also takes place in other spheres of life, such as the workplace. This paper examines the role of residential segregation in workplace segregation among recently arrived immigrants. By using unique longitudinal register data from Sweden, we show that the role of residential segregation in workplace segregation differs in an important way for immigrant men and immigrant women

    Relations between residential and workplace segregation among newly arrived immigrant men and women

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    The research leading to these results has received funding from the Estonian Research Council (Institutional Research Grant IUT2-17 on Spatial Population Mobility and Geographical Changes in Urban Regions); the Estonian Science Foundation (grant no. 8774 and 9247); the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 615159 (ERC Consolidator Grant DEPRIVEDHOODS, Socio-spatial inequality, deprived neighbourhoods, and neighbourhood effects); and the Marie Curie Programme under the European Union's Seventh Framework Programme (FP/2007-2013) / Career Integration Grant n. PCIG10-GA-2011-303728 (CIG Grant NBHCHOICE, Neighbourhood choice, neighbourhood sorting, and neighbourhood effects).Contemporary cities are becoming more and more diverse in population as a result of immigration. Research shows that while residential neighborhoods are becoming ethnically more diverse within cities, residential segregation from natives has overall remained persistently high. High levels of segregation are often seen as negative, preventing the integration of immigrants into their host society and having a negative impact on people's lives. Where as most studies of segregation deal with residential neighborhoods, this paper investigates segregation at workplaces for newly arrived immigrant men and women from the Global South to Sweden. By using the domain approach, we focus on the relationship between workplace segregation, residential segregation, and the ethnic composition of households. Using longitudinal register data from Sweden, we find that residential segregation is much weaker related to workplace segregation than revealed by studies using cross-sectional data. Furthermore, the residential context is not an important factor in explaining workplace segregation for immigrant men. The most important factors shaping workplace segregation pertain to economic sector and city size.Publisher PDFPeer reviewe

    Investigating star formation in the young open cluster NGC 6383

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    By studying young open clusters, the mechanisms important for star formation over several Myr can be examined. For example, accretion rate as a function of rotational velocity can be investigated. Similarly, sequential star formation triggered by massive stars with high mass-loss rates can be studied in detail. We identified and characterized probable members of NGC 6383, as well as determined cluster parameters. New Stromgren uvby CCD photometry, obtained by us, is presented. This new data, together with Johnson UBV and 2MASS data in the NIR, was used to investigate characteristics of pre- as well as zero age main sequence cluster members. We present Stromgren uvby CCD photometry for 272 stars in the field of NGC 6383 and derive its reddening, E(b-y)=0.21(4)mag, as well as distance, d=1.7(3)kpc from the Sun. Several stars with NIR excess and objects in the domain of the classical Herbig Ae/Be and T Tauri stars were detected. Two previously known variables were identified as rapidly-rotating PMS stars. The field population is clearly separated from the probable members in the color-magnitude diagram. NGC 6383 is a young open cluster, with an age of less than 4 Myr, undergoing continuous star formation. True pre-main sequence members might be found down to absolute magnitudes of +6mag, with a variety of rotational velocities and stellar activities.Comment: 7 pages, 6 figures, accepted by A&

    Carbon dioxide emissions from reed canary grass during two growing seasons after restoration of an abandoned agricultural peat soil

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    Reed canary grass (RCG) can be a suitable energy crop on abandoned agricultural peatland as it can be harvested for more than 10 years without re-establishment, and nutrient recycling to rhizomes lowers the fertilizer demand. A field near Mala in Sweden was restored by improving drainage and sowing RCG in 2010. In the first growing season, CO2 emissions from the soil were lower and groundwater level and soil water content higher for the RCG field than for a nearby unrestored field. Possible reasons were peat compaction by agricultural machinery in the restored field and higher transpiration and respiration from vegetation in the unrestored field. In the second growing season, the groundwater level was raised in some restored plots and CO2 emissions and RCG growth were found to be unaffected by this practice

    Propagation of ionizing radiation in HII regions: the effects of optically thick density fluctuations

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    The accepted explanation of the observed dichotomy of two orders of magnitude between in situ measurements of electron density in HII regions, derived from emission line ratios, and average measurements based on integrated emission measure, is the inhomogeneity of the ionized medium. This is expressed as a "filling factor", the volume ratio of dense to tenuous gas, measured with values of order 10^-3. Implicit in the filling factor model as normally used, is the assumption that the clumps of dense gas are optically thin to ionizing radiation. Here we explore implications of assuming the contrary: that the clumps are optically thick. A first consequence is the presence within HII regions of a major fraction of neutral hydrogen. We estimate the mean H^o/H^+ ratio for a population of HII regions in the spiral galaxy NGC 1530 to be the order of 10, and support this inference using dynamical arguments. The optically thick clumpy models allow a significant fraction of the photons generated by the ionizing stars to escape from their HII region. We show, by comparing model predictions with observations, that these models give an account at least as good as, and probably better than that of conventional models, of the radial surface brightness distribution and of selected spectral line diagnostics for physical conditions within HII regions. These models explain how an HII region can appear, from its line ratios, to be ionization bounded, yet permit a major fraction of its ionizing photons to escape.Comment: 9 pages, 7 figures (2 of them in colours), accepted for publication in A&

    The high-energy environment in the super-earth system CoRoT-7

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    High-energy irradiation of exoplanets has been identified to be a key influence on the stability of these planets' atmospheres. So far, irradiation-driven mass-loss has been observed only in two Hot Jupiters, and the observational data remain even more sparse in the super-earth regime. We present an investigation of the high-energy emission in the CoRoT-7 system, which hosts the first known transiting super-earth. To characterize the high-energy XUV radiation field into which the rocky planets CoRoT-7b and CoRoT-7c are immersed, we analyzed a 25 ks XMM-Newton observation of the host star. Our analysis yields the first clear (3.5 sigma) X-ray detection of CoRoT-7. We determine a coronal temperature of ca. 3 MK and an X-ray luminosity of 3*10^28 erg/s. The level of XUV irradiation on CoRoT-7b amounts to ca. 37000 erg/cm^2/s. Current theories for planetary evaporation can only provide an order-of-magnitude estimate for the planetary mass loss; assuming that CoRoT-7b has formed as a rocky planet, we estimate that CoRoT-7b evaporates at a rate of about 1.3*10^11 g/s and has lost ca. 4-10 earth masses in total.Comment: 5 pages, accepted for publication by Astronomy & Astrophysic

    Periodic orbits in the restricted three-body problem and Arnold's J+J^+-invariant

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    We apply Arnold's theory of generic smooth plane curves to Stark-Zeeman systems. This is a class of Hamiltonian dynamical systems that describes the dynamics of an electron in an external electric and magnetic field, and includes many systems from celestial mechanics. Based on Arnold's J+J^+-invariant, we introduce invariants of periodic orbits in planar Stark-Zeeman systems and study their behaviour.Comment: 36 Pages, 16 Figure

    Properties of the 5- state at 839 keV in 176Lu and the s-process branching at A = 176

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    The s-process branching at mass number A = 176 depends on the coupling between the high-K ground state and a low-lying low-K isomer in 176Lu. This coupling is based on electromagnetic transitions via intermediate states at higher energies. The properties of the lowest experimentally confirmed intermediate state at 839 keV are reviewed, and the transition rate between low-K and high-K states under stellar conditions is calculated on the basis of new experimental data for the 839 keV state. Properties of further candidates for intermediate states are briefly analyzed. It is found that the coupling between the high-K ground state and the low-K isomer in 176Lu is at least one order of magnitude stronger than previously assumed leading to crucial consequences for the interpretation of the 176Lu/176Hf pair as an s-process thermometer.Comment: 11 pages, 4 figures accepted for publication in Phys. Rev.

    Photometric signatures of multiple stellar populations in Galactic globular clusters

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    We have calculated synthetic spectra for typical chemical element mixtures (i.e., a standard alpha-enhanced distribution, and distributions displaying CN and ONa anticorrelations) found in the various subpopulations harboured by Galactic globular clusters. From the spectra we have determined bolometric corrections to the standard Johnson-Cousins and Stroemgren filters, and finally predicted colours. These bolometric corrections and colour-transformations, coupled to our theoretical isochrones with the appropriate chemical composition, provide a complete and self-consistent set of theoretical predictions for the effect of abundance variations on the observed cluster CMD. CNO abundance variations affect mainly wavelengths shorter than 400 nm, due to the arise of molecular absorption bands in cooler atmospheres. As a consequence, colour and magnitude changes are largest in the blue filters, independently of using broad or intermediate bandpasses. Colour-magnitude diagrams involving uvy and UB filters (and their various possible colour combinations) are thus the ones best suited to infer photometrically the presence of multiple stellar generations in individual clusters. They are particularly sensitive to variations in the N abundance, with the largest variations affecting the Red Giant Branch (RGB) and lower Main Sequence (MS). BVI diagrams are expected to display multiple sequences only if the different populations are characterized by variations of the C+N+O sum and helium abundance, that lead to changes in luminosity and effective temperature, but leave the flux distribution above 400 nm practically unaffected. A variation of just the helium abundance, up to the level we investigate here, affects exclusively the interior structure of stars, and is largely irrelevant for the atmospheric structure and the resulting flux distribution in the whole wavelength range spanned by our analysis.Comment: 15 pages, 15 figures, submitted to A&A, referee comments addresse
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