307 research outputs found

    The Formation and Evolution of the First Massive Black Holes

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    The first massive astrophysical black holes likely formed at high redshifts (z>10) at the centers of low mass (~10^6 Msun) dark matter concentrations. These black holes grow by mergers and gas accretion, evolve into the population of bright quasars observed at lower redshifts, and eventually leave the supermassive black hole remnants that are ubiquitous at the centers of galaxies in the nearby universe. The astrophysical processes responsible for the formation of the earliest seed black holes are poorly understood. The purpose of this review is threefold: (1) to describe theoretical expectations for the formation and growth of the earliest black holes within the general paradigm of hierarchical cold dark matter cosmologies, (2) to summarize several relevant recent observations that have implications for the formation of the earliest black holes, and (3) to look into the future and assess the power of forthcoming observations to probe the physics of the first active galactic nuclei.Comment: 39 pages, review for "Supermassive Black Holes in the Distant Universe", Ed. A. J. Barger, Kluwer Academic Publisher

    Measurement of the inclusive and dijet cross-sections of b-jets in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

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    The inclusive and dijet production cross-sections have been measured for jets containing b-hadrons (b-jets) in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV, using the ATLAS detector at the LHC. The measurements use data corresponding to an integrated luminosity of 34 pb^-1. The b-jets are identified using either a lifetime-based method, where secondary decay vertices of b-hadrons in jets are reconstructed using information from the tracking detectors, or a muon-based method where the presence of a muon is used to identify semileptonic decays of b-hadrons inside jets. The inclusive b-jet cross-section is measured as a function of transverse momentum in the range 20 < pT < 400 GeV and rapidity in the range |y| < 2.1. The bbbar-dijet cross-section is measured as a function of the dijet invariant mass in the range 110 < m_jj < 760 GeV, the azimuthal angle difference between the two jets and the angular variable chi in two dijet mass regions. The results are compared with next-to-leading-order QCD predictions. Good agreement is observed between the measured cross-sections and the predictions obtained using POWHEG + Pythia. MC@NLO + Herwig shows good agreement with the measured bbbar-dijet cross-section. However, it does not reproduce the measured inclusive cross-section well, particularly for central b-jets with large transverse momenta.Comment: 10 pages plus author list (21 pages total), 8 figures, 1 table, final version published in European Physical Journal

    The Formation of the First Massive Black Holes

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    Supermassive black holes (SMBHs) are common in local galactic nuclei, and SMBHs as massive as several billion solar masses already exist at redshift z=6. These earliest SMBHs may grow by the combination of radiation-pressure-limited accretion and mergers of stellar-mass seed BHs, left behind by the first generation of metal-free stars, or may be formed by more rapid direct collapse of gas in rare special environments where dense gas can accumulate without first fragmenting into stars. This chapter offers a review of these two competing scenarios, as well as some more exotic alternative ideas. It also briefly discusses how the different models may be distinguished in the future by observations with JWST, (e)LISA and other instruments.Comment: 47 pages with 306 references; this review is a chapter in "The First Galaxies - Theoretical Predictions and Observational Clues", Springer Astrophysics and Space Science Library, Eds. T. Wiklind, V. Bromm & B. Mobasher, in pres

    Mediators of the relationship between attachment and dispositional mindfulness in adolescents

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    ObjectivesConverging studies have confirmed a robust relationship between attachment and mindfulness, leading to the proposition that dispositional mindfulness originates from early interpersonal relationships. Despite this assertion, few studies have examined these relationships in adolescents and young adults. Theoretical linkages between mindfulness, attachment, relationships, and self-regulation suggest that attachment may be linked to mindfulness via self-regulatory capacity. This study examined the direct effect of attachment on dispositional mindfulness in adolescents and young adults, as well as indirect effects via attentional control and emotion regulation.MethodsParticipants were 421 adolescents and young people age 12–24 years (M = 17, SD = 4.10). They completed a self-report survey measuring attachment anxiety, attachment avoidance, dispositional mindfulness, attentional control (AC), and emotion regulation (ER).ResultsThere was a moderate effect of attachment anxiety 95% CI [− 1.45, − 0.93], and a small effect of attachment avoidance 95% CI [− 1.27, − 0.44] on mindfulness. Attachment anxiety was indirectly related to mindfulness via AC, 95% CI [− 0.32, − 10], and ER, [− 0.80, − 0.41], as was attachment avoidance (AC, 95% CI [− 44, − 0.10], ER, 95% CI [− 0.52, − 0.19]. Serial mediation analyses revealed serial paths from AC through ER and ER through AC with small effect sizes relative to individual mediators.ConclusionsLevels of dispositional mindfulness in adolescents were linked to attachment insecurity dimensions through attention control and emotion regulation. Attachment dimension-specific differences were noted; for the anxiety dimension, emotion regulation exerts a stronger mediating effect

    Adult Romantic Attachment, Negative Emotionality, and Depressive Symptoms in Middle Aged Men: A Multivariate Genetic Analysis

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    Adult romantic attachment styles reflect ways of relating in close relationships and are associated with depression and negative emotionality. We estimated the extent to which dimensions of romantic attachment and negative emotionality share genetic or environmental risk factors in 1,237 middle-aged men in the Vietnam Era Twin Study of Aging (VETSA). A common genetic factor largely explained the covariance between attachment-related anxiety, attachment-related avoidance, depressive symptoms, and two measures of negative emotionality: Stress-Reaction (anxiety), and Alienation. Multivariate results supported genetic and environmental differences in attachment. Attachment-related anxiety and attachment-related avoidance were each influenced by additional genetic factors not shared with other measures; the genetic correlation between the attachment measure-specific genetic factors was 0.41, indicating some, but not complete overlap of genetic factors. Genetically informative longitudinal studies on attachment relationship dimensions can help to illuminate the role of relationship-based risk factors in healthy aging

    Networks of Emotion Concepts

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    The aim of this work was to study the similarity network and hierarchical clustering of Finnish emotion concepts. Native speakers of Finnish evaluated similarity between the 50 most frequently used Finnish words describing emotional experiences. We hypothesized that methods developed within network theory, such as identifying clusters and specific local network structures, can reveal structures that would be difficult to discover using traditional methods such as multidimensional scaling (MDS) and ordinary cluster analysis. The concepts divided into three main clusters, which can be described as negative, positive, and surprise. Negative and positive clusters divided further into meaningful sub-clusters, corresponding to those found in previous studies. Importantly, this method allowed the same concept to be a member in more than one cluster. Our results suggest that studying particular network structures that do not fit into a low-dimensional description can shed additional light on why subjects evaluate certain concepts as similar. To encourage the use of network methods in analyzing similarity data, we provide the analysis software for free use (http://www.becs.tkk.fi/similaritynets/)

    Cultural Aspects of Attachment Anxiety, Avoidance, and Life Satisfaction: Comparing the US and Turkey

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    Attachment insecurity can interfere with the experience, expression, and benefits of positive emotions, including happiness and life satisfaction (LS). However, both the pattern and effects of insecure attachment orientations on LS vary across cultures. Considering that attachment anxiety is higher in collectivist cultures and attachment avoidance is relatively high in individualistic cultures, the present chapter elaborates on the idea that anxious and avoidant attachment would have varying effects on LS in individualistic and collectivistic cultural contexts. Study 1 (N = 2456) involved a community sample of married couples in Turkey and demonstrated that attachment avoidance was a stronger predictor of LS than attachment anxiety in Turkish collectivist context. Study 2 tested the hypothesis that the roles of attachment anxiety and avoidance in predicting LS would vary between collectivistic and individualistic cultures. Mothers’ adult attachment dimensions and LS in Turkey (N = 89) and the United States (N = 91) were measured. As expected, results indicated that LS was predicted only by attachment avoidance in Turkey and by attachment anxiety in the United States. These findings are in line with the cultural fit hypothesis, suggesting that culturally incongruent attachment orientations have a stronger negative impact on individuals’ LS

    Population transcriptomics of Drosophila melanogaster females

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    <p>Abstract</p> <p>Background</p> <p>Variation at the level of gene expression is abundant in natural populations and is thought to contribute to the adaptive divergence of populations and species. Gene expression also differs considerably between males and females. Here we report a microarray analysis of gene expression variation among females of 16 <it>Drosophila </it><it>melanogaster </it>strains derived from natural populations, including eight strains from the putative ancestral range in sub-Saharan Africa and eight strains from Europe. Gene expression variation among males of the same strains was reported previously.</p> <p>Results</p> <p>We detected relatively low levels of expression polymorphism within populations, but much higher expression divergence between populations. A total of 569 genes showed a significant expression difference between the African and European populations at a false discovery rate of 5%. Genes with significant over-expression in Europe included the insecticide resistance gene <it>Cyp6g1</it>, as well as genes involved in proteolysis and olfaction. Genes with functions in carbohydrate metabolism and vision were significantly over-expressed in the African population. There was little overlap between genes expressed differently between populations in females and males.</p> <p>Conclusions</p> <p>Our results suggest that adaptive changes in gene expression have accompanied the out-of-Africa migration of <it>D. melanogaster</it>. Comparison of female and male expression data indicates that the vast majority of genes differing in expression between populations do so in only one sex and suggests that most regulatory adaptation has been sex-specific.</p

    Exploring attachment to the "homeland" and its association with heritage culture identification

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    Conceptualisations of attachment to one’s nation of origin reflecting a symbolic caregiver can be found cross-culturally in literature, art, and language. Despite its prevalence, the relationship with one’s nation has not been investigated empirically in terms of an attachment theory framework. Two studies employed an attachment theory approach to investigate the construct validity of symbolic attachment to one’s nation of origin, and its association with acculturation (operationalized as heritage and mainstream culture identification). Results for Study 1 indicated a three-factor structure of nation attachment; the factors were labelled secure-preoccupied, fearful, and dismissive nation attachment. Hierarchical linear modelling was employed to control for differing cultures across participants. Secure-preoccupied nation attachment was a significant predictor of increased heritage culture identification for participants residing in their country of birth, whilst dismissive nation attachment was a significant predictor of decreased heritage culture identification for international migrants. Securepreoccupied nation attachment was also associated with higher levels of subjective-wellbeing. Study 2 further confirmed the validity of the nation attachment construct through confirmatory factor analysis; the three-factor model adequately fit the data. Similar to the results of Study 1, secure-preoccupied nation attachment was associated with increased levels of heritage culture identification and psychological well-being. Implications of the tripartite model of nation attachment for identity and well-being will be discussed
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