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Sökning: WFRF:(Koposov Roman A.)

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  • Smiljanic, R., et al. (författare)
  • The Gaia-ESO Survey: The analysis of high-resolution UVES spectra of FGK-type stars
  • 2014
  • Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 570
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. The ongoing Gaia-ESO Public Spectroscopic Survey is using FLAMES at the VLT to obtain high-quality medium-resolution Giraffe spectra for about 10(5) stars and high-resolution UVES spectra for about 5000 stars. With UVES, the Survey has already observed 1447 FGK-type stars. Aims. These UVES spectra are analyzed in parallel by several state-of-the-art methodologies. Our aim is to present how these analyses were implemented, to discuss their results, and to describe how a final recommended parameter scale is defined. We also discuss the precision (method-to-method dispersion) and accuracy (biases with respect to the reference values) of the final parameters. These results are part of the Gaia-ESO second internal release and will be part of its first public release of advanced data products. Methods. The final parameter scale is tied to the scale defined by the Gaia benchmark stars, a set of stars with fundamental atmospheric parameters. In addition, a set of open and globular clusters is used to evaluate the physical soundness of the results. Each of the implemented methodologies is judged against the benchmark stars to define weights in three different regions of the parameter space. The final recommended results are the weighted medians of those from the individual methods. Results. The recommended results successfully reproduce the atmospheric parameters of the benchmark stars and the expected T-eff-log g relation of the calibrating clusters. Atmospheric parameters and abundances have been determined for 1301 FGK-type stars observed with UVES. The median of the method-to-method dispersion of the atmospheric parameters is 55K for T-eff, 0.13dex for log g and 0.07 dex for [Fe/H]. Systematic biases are estimated to be between 50-100 K for T-eff, 0.10-0.25 dex for log g and 0.05-0.10 dex for [Fe/H]. Abundances for 24 elements were derived: C, N, O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Mo, Ba, Nd, and Eu. The typical method-to-method dispersion of the abundances varies between 0.10 and 0.20 dex. Conclusions. The Gaia-ESO sample of high-resolution spectra of FGK-type stars will be among the largest of its kind analyzed in a homogeneous way. The extensive list of elemental abundances derived in these stars will enable significant advances in the areas of stellar evolution and Milky Way formation and evolution.
  • Jacobson, H. R., et al. (författare)
  • The Gaia -ESO Survey : Probes of the inner disk abundance gradient
  • 2016
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 591
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. The nature of the metallicity gradient inside the solar circle (RGC <8 kpc) is poorly understood, but studies of Cepheids and a small sample of open clusters suggest that it steepens in the inner disk. Aims. We investigate the metallicity gradient of the inner disk using a sample of inner disk open clusters that is three times larger than has previously been studied in the literature to better characterize the gradient in this part of the disk. Methods. We used the Gaia-ESO Survey (GES) [Fe/H] values and stellar parameters for stars in 12 open clusters in the inner disk from GES-UVES data. Cluster mean [Fe/H] values were determined based on a membership analysis for each cluster. Where necessary, distances and ages to clusters were determined via comparison to theoretical isochrones. Results. The GES open clusters exhibit a radial metallicity gradient of -0.10 ± 0.02 dex kpc-1, consistent with the gradient measured by other literature studies of field red giant stars and open clusters in the range RGC ~ 6-12 kpc. We also measure a trend of increasing [Fe/H] with increasing cluster age, as has also been found in the literature. Conclusions. We find no evidence for a steepening of the inner disk metallicity gradient inside the solar circle as earlier studies indicated. The age-metallicity relation shown by the clusters is consistent with that predicted by chemical evolution models that include the effects of radial migration, but a more detailed comparison between cluster observations and models would be premature.
  • Tang, B., et al. (författare)
  • The Gaia-ESO survey : the inner disk intermediate-age open cluster NGC 6802
  • 2017
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 601
  • Tidskriftsartikel (refereegranskat)abstract
    • Milky Way open clusters are very diverse in terms of age, chemical composition, and kinematic properties. Intermediate-age and old open clusters are less common, and it is even harder to find them inside the solar Galactocentric radius, due to the high mortality rate and strong extinction inside this region. NGC 6802 is one of the inner disk open clusters (IOCs) observed by the Gaia-ESO survey (GES). This cluster is an important target for calibrating the abundances derived in the survey due to the kinematic and chemical homogeneity of the members in open clusters. Using the measurements from Gaia-ESO internal data release 4 (iDR4), we identify 95 main-sequence dwarfs as cluster members from the GIRAFFE target list, and eight giants as cluster members from the UVES target list. The dwarf cluster members have a median radial velocity of 13.6 +/- 1.9 km s(-1), while the giant cluster members have a median radial velocity of 12.0 +/- 0.9 km s(-1) and a median [Fe/H] of 0.10 +/- 0.02 dex. The color-magnitude diagram of these cluster members suggests an age of 0.9 +/- 0.1 Gyr, with (m - M)(0) = 11.4 and E(B - V) = 0.86. We perform the first detailed chemical abundance analysis of NGC 6802, including 27 elemental species. To gain a more general picture about IOCs, the measurements of NGC 6802 are compared with those of other IOCs previously studied by GES, that is, NGC 4815, Trumpler 20, NGC 6705, and Berkeley 81. NGC 6802 shows similar C, N, Na, and Al abundances as other IOCs. These elements are compared with nucleosynthetic models as a function of cluster turn-off mass. The alpha, iron-peak, and neutron-capture elements are also explored in a self-consistent way.
  • Donati, P., et al. (författare)
  • The Gaia-ESO Survey : Reevaluation of the parameters of the open cluster Trumpler 20 using photometry and spectroscopy
  • 2014
  • Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 561, s. A94-
  • Tidskriftsartikel (refereegranskat)abstract
    • Trumpler 20 is an old open cluster (OC) located toward the Galactic centre, at about 3 kpc from the Sun and similar to 7 kpc from the Galactic centre. Its position makes this cluster particularly interesting in the framework of the chemical properties of the Galactic disc because very few old OCs reside in the inner part of the disc. For this reason it has been selected as a cluster target of the Gaia-ESO Survey, and spectra of many stars in the main-sequence and red-clump phases are now available. Moreover, although it has been studied by several authors in the past, no consensus on the evolutionary status of Tr 20 has been reached. The heavy contamination of field stars (the line of sight of Tr 20 crosses the Carina spiral arm) complicates a correct interpretation. Another interesting aspect of the cluster is that it shows a broadened main-sequence turn-off and a prominent and extended red-clump, characteristics that are not easily explained by classical evolutionary models. Exploiting both spectroscopic information from the Gaia-ESO Survey (and the ESO archive) and literature photometry, we obtain a detailed and accurate analysis of the properties of the cluster. We make use of the first accurate metallicity measurement ever obtained from several spectra of red clump stars, and of cluster membership determination using radial velocities. According to the evolutionary models adopted, we find that Tr 20 has an age in the range 1.35-1.66 Gyr, an average reddening E(B - V) in the range 0.31-0.35 mag, and a distance modulus (m - M)(0) between 12.64 and 12.72 mag. The spectroscopic metallicity is [Fe/H] = +0.17 dex. We discuss the structural properties of the object and constrain possible hypotheses for its broadened upper main sequence by estimating the effect of differential reddening and its extended red clump.
  • Isaksson, Johan, et al. (författare)
  • Risky sexual behaviour among Russian adolescents : association with internalizing and externalizing symptoms
  • 2021
  • Ingår i: Child and Adolescent Psychiatry and Mental Health. - : Springer Nature. - 1753-2000 .- 1753-2000. ; 15:1
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Risky sexual behaviour (RSB) is regarded as a major health problem during adolescence. Russia has one of the highest rates of teenage pregnancy, abortion and newly diagnosed HIV infections in the world, but research on RSB in Russian youth has been limited. To address this deficit, this study examined the role of several factors, including internalizing and externalizing symptoms, in RSB among Russian adolescents.METHODS: Self-reported data were collected from 2573 Russian adolescents aged 13-17 years old (59.4 % girls; Mean age = 14.89) regarding RSB (unprotected sex, early pregnancy, multiple sexual partners and substance use during sexual encounters). Information was also obtained on externalizing (conduct problems and delinquent behaviour) and internalizing (depression, anxiety and posttraumatic stress) symptoms, as well as interpersonal risk and protective factors (affiliation with delinquent peers, parental involvement and teacher support). Hierarchical multiple binary logistic regression analysis was used to examine the associations between these variables and RSB.RESULTS: Boys reported engaging in more RSB than girls. Externalizing symptoms and affiliation with delinquent peers were most strongly associated with RSB, whereas symptoms of anxiety were negatively associated with RSB. There was an interaction effect for sex and affiliation with delinquent peers on RSB with boys reporting RSB when having more delinquent peers. Neither parental involvement nor teacher support were protective against RSB.CONCLUSIONS: Early detection of and interventions for RSB and associated externalizing symptoms may be important for adolescent physical and mental wellbeing. Affiliation with delinquent peers should, especially among boys, be regarded as a risk marker for RSB.
  • Magrini, L., et al. (författare)
  • The Gaia-ESO Survey: Abundance ratios in the inner-disk open clusters Trumpler 20, NGC 4815, NGC 6705
  • 2014
  • Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 563
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. Open clusters are key tools to study the spatial distribution of abundances in the disk and their evolution with time. Aims. Using the first release of stellar parameters and abundances of the Gaia-ESO Survey, we analyse the chemical properties of stars in three old/intermediate-age open clusters, namely NGC 6705, NGC 4815, and Trumpler 20, which are all located in the inner part of the Galactic disk at Galactocentric radius R-GC similar to 7 kpc. We aim to prove their homogeneity and to compare them with the field population. Methods. We study the abundance ratios of elements belonging to two different nucleosynthetic channels: alpha-elements and iron-peak elements. For each element, we analyse the internal chemical homogeneity of cluster members, and we compare the cumulative distributions of cluster abundance ratios with those of solar neighbourhood turn-off stars and of inner-disk/bulge giants. We compare the abundance ratios of field and cluster stars with two chemical evolution models that predict different alpha-enhancement dependences on the Galactocentric distance due to different assumptions on the infall and star-formation rates. Results. The main results can be summarised as follows: i) cluster members are chemically homogeneous within 3 sigma in all analysed elements; ii) the three clusters have comparable [El/Fe] patterns within similar to 1 sigma, but they differ in their global metal content [El/H] with NGC 4815 having the lowest metallicity; their [El/Fe] ratios show differences and analogies with those of the field population, in both the solar neighbourhood and the bulge/inner disk; iii) comparing the abundance ratios with the results of two chemical evolution models and with field star abundance distributions, we find that the abundance ratios of Mg, Ni, and Ca in NGC 6705 might require an inner birthplace, implying a subsequent variation in its R-GC during its lifetime, which is consistent with previous orbit determination. Conclusions. Using the results of the first internal data release, we show the potential of the Gaia-ESO Survey through a homogeneous and detailed analysis of the cluster versus field populations to reveal the chemical structure of our Galaxy using a completely uniform analysis of different populations. We verify that the Gaia-ESO Survey data are able to identify the unique chemical properties of each cluster by pinpointing the composition of the interstellar medium at the epoch and place of formation. The full dataset of the Gaia-ESO Survey is a superlative tool to constrain the chemical evolution of our Galaxy by disentangling different formation and evolution scenarios.
  • Väfors Fritz, Marie, et al. (författare)
  • Psychopathy and violence in juvenile delinquents : What are the associated factors?
  • 2008
  • Ingår i: International Journal of Law and Psychiatry. - 0160-2527 .- 1873-6386. ; 31:3, s. 272-279
  • Tidskriftsartikel (refereegranskat)abstract
    • The purpose of the present study was a) to examine the discriminative power of the Antisocial Process Screening Device (APSD), aggressive traits, impulsiveness, antisocial attitudes and alcohol-related problems between subgroups of Russian juvenile delinquents (n = 175) with low versus high levels of violent behavior; and b) to compare the predictive value of these variables in two subgroups defined by higher versus lower levels of psychopathic traits. Results demonstrated that the APSD score, traits of physical aggression and alcohol-related problems were able to discriminate between groups with various levels of violence. Furthermore, the level of violence was the only variant factor when comparing levels of psychopathy. Finally, different sets of predictors emerged for the group with higher versus lower psychopathy scores. The results are discussed in relation to specific features of psychopathy and environmental factors in general and the use of alcohol in particular.
  • Ruchkin, Vladislav V, et al. (författare)
  • Platelet MAO-B, personality, and psychopathology
  • 2005
  • Ingår i: Journal of Abnormal Psychology. - 0021-843X .- 1939-1846. ; 114:3, s. 477-482
  • Tidskriftsartikel (refereegranskat)abstract
    • The article investigates the relationships between platelet monoamine oxidase-B (MAO-B) activity, personality, and psychopathology (Diagnostic and Statistical Manual of Mental Disorders [4th ed.; American Psychiatric Association, 1994] diagnoses. These relationships were assessed in 178 incarcerated male juvenile delinquents. Even after controlling for smoking, the authors found that both Internalizing and Externalizing Psychopathology were negatively related to MAO-B activity. In the final reduced model, novelty seeking fully mediated the relationships between MAO-B and Externalizing Psychopathology but not between MAO-B and Internalizing Psychopathology. It was hypothesized that low platelet MAO-B activity does not directly predispose individuals to psychopathology but is related to specific personality traits, which in turn represent a vulnerability factor for psychopathology. Future studies should help clarify the nature of the relationships between personality, biological markers, and psychopathology.
  • Stickley, Andrew, et al. (författare)
  • Binge drinking among adolescents in Russia : Prevalence, risk and protective factors
  • 2013
  • Ingår i: Addictive Behaviours. - 0306-4603 .- 1873-6327. ; 38:4, s. 1988-1995
  • Tidskriftsartikel (refereegranskat)abstract
    • Despite evidence that alcohol misuse has been having an increasingly detrimental effect on adolescent wellbeing in Russia in recent years this phenomenon has been little researched. Using data from 2112 children from the Arkhangelsk Social and Health Assessment (SAHA) 2003, this study examined which factors acted as 'risk' or 'protective' factors for adolescent binge drinking within three domains we termed the 'family environment', the 'alcohol environment' and 'deviant behaviour'. The results showed that in the presence of comparatively moderate levels of binge drinking among both boys and girls, being able to access alcohol easily, being unaware of the risks of binge drinking and having peers who consumed alcohol increased the risk of adolescent binge drinking - as did playing truant, smoking and marijuana use, while parental warmth was protective against binge drinking for girls. Our finding that risk and protective factors occur across domains suggests that any interventions targeted against adolescent binge drinking may need to simultaneously focus on risk behaviours in different domains, while at the same time, broader social policy should act to limit the availability of alcohol to adolescents in Russia more generally.
  • Grigorenko, Elena L., et al. (författare)
  • Aggressive Behavior, Related Conduct Problems, and Variation in Genes Affecting Dopamine Turnover
  • 2010
  • Ingår i: Aggressive Behavior. - 0096-140X .- 1098-2337. ; 36:3, s. 158-176
  • Tidskriftsartikel (refereegranskat)abstract
    • A number of dopamine-related genes have been implicated in the etiology of violent behavior and conduct problems. Of these genes, the ones that code for the enzymes that influence the turnover of dopamine (DA) have received the most attention. In this study, we investigated 12 genetic polymorphisms in four genes involved with DA functioning (COMT, MAOA and MAOB, and D beta H in 179 incarcerated male Russian adolescents and two groups of matched controls: boys without criminal records referred to by their teachers as (a) "troubled-behavior-free" boys, n = 182; and (b) "troubled-behavior" boys, n = 60. The participants were classified as (1) being incarcerated or not, (2) having the DSM-IV diagnosis of conduct disorder (CD) or not, and (3) having committed violent or nonviolent crimes (for the incarcerated individuals only). The findings indicate that, although no single genetic variant in any of the four genes differentiated individuals in the investigated groups, various linear combinations (i.e., haplotypes) and nonlinear combinations (i.e., interactions between variants within and across genes) of genetic variants resulted in informative and robust classifications for two of the three groupings. These combinations of genetic variants differentiated individuals in incarceration vs. nonincarcerated and CD vs. no-CD groups; no informative combinations were established consistently for the grouping by crime within the incarcerated individuals. This study underscores the importance of considering multiple rather than single markers within candidate genes and their additive and interactive combinations, both with themselves and with nongenetic indicators, while attempting to understand the genetic background of such complex behaviors as serious conduct problems.
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