Galaxy properties and the cosmic web in simulations Metuki, Ofer; Libeskind, Noam I.; Hoffman, Yehuda ...
Monthly notices of the Royal Astronomical Society,
01/2015, Letnik:
446, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We seek to understand the relationship between galaxy properties and their local environment, which calls for a proper formulation of the notion of environment. We analyse the Galaxies-Intergalactic ...Medium Interaction Calculation suite of cosmological hydrodynamical simulations within the framework of the cosmic web as formulated by Hoffman et al., focusing on properties of simulated dark matter haloes and luminous galaxies with respect to voids, sheets, filaments, and knots -- the four elements of the cosmic web. We find that the mass functions of haloes depend on environment, which drives other environmental dependence of galaxy formation. The web shapes the halo mass function, and through the strong dependence of the galaxy properties on the mass of their host haloes, it also shapes the galaxy-(web) environment dependence.
To assess real-time 3-dimensional echocardiography (RT3DE)-derived left ventricular (LV) systolic dyssynchrony parameters: (1) normal values, (2) characteristics in patients with heart failure (HF) ...and a wide or narrow QRS complex, (3) interobserver and intraobserver variability with current state of the art RT3DE hardware and software technology, and (4) incremental value in patients with HF who receive cardiac resynchronization therapy (CRT).
The study involved 84 patients with HF (mean age 54 +/- 15 years, 50 men) and 60 healthy volunteers (mean age 41 +/- 15 years, 36 men). Semiautomated LV endocardial border tracking was used to calculate regional time-to-minimum systolic volume and to generate parametric maps and the systolic dyssynchrony index (SDI), defined as the standard deviation of time-to-minimum systolic volume of the 16 LV segments expressed in percentage of R-R duration.
The volume rate of the RT3DE datasets in patients with HF was 31 +/- 9 Hz (range 15-42 Hz). The normal value of the SDI was 4.1% +/- 2.2% (range <1.0%-8.9%). Patients with HF had a larger SDI (13.4% +/- 8.1%, P < .001). There was only a weak correlation (r2 = 0.07, P < .05) between the QRS duration and the SDI. Interobserver interclass correlation and variability of the SDI depended on image quality (good: 0.993 and 9%, moderate: 0.907 and 16%, respectively). Interobserver agreement for the identification of the most delayed LV segment depended on image quality (good: 90%, moderate: 76%). Thirty-nine patients underwent CRT. At the 12-month follow-up, LV volumetric responders had a significant reduction in the SDI (16.3% +/- 3.3% to 7.7% +/- 2.4%, P < .001).
With state of the art technology, RT3DE allows reproducible assessment of LV systolic dyssynchrony, which may be useful to identify potential responders to CRT.
Purpose of the study: The purpose of the study was to develop and assess whether a leadership skills development model, which integrates six valid conceptual constructs, will develop enhanced ...leadership skills in an African-based fast-moving consumer goods business network.Design/methodology/approach: The six-construct model is predicated on the literature review, which was empirically tested. Thus, the study selected a pragmatic approach and followed up with an explanatory sequential design typology. Moreover, this study adopted a quantitative, cross-sectional survey research methodology, while an online survey was administered to collect primary data from the Kwaden Group. Inferential statistics were also employed so as to appropriately examine the validity and reliability of the constructs. Finally, a qualitative phenomenological research approach was utilised to collect primary data from key decision-makers within the African fast-moving consumer goods business network via structured face-to- face interviews.Findings: The study provides a theoretically relevant and empirically validated leadership skills development model amendable to an African fast-moving consumer goods business network. Additionally, a confirmatory factor analysis confirmed a good model fit for the leadership skills development model. It was also established that leadership skills development should be multilevel, which infers that participants should have the opportunity to develop multifaceted leadership skills and that such leadership capabilities should be a primary company objective.Recommendations/value: The leadership skills development model, if adopted by an organisation, will result in a leadership skills development initiative being established on theoretically relevant and empirically validated constructs.Managerial implications: This dedicated approach should assist organisations in developing the necessary leadership skills among their personnel so as to enhance the company’s leadership capacity and ultimately improve business potential and profitability. This perspective should also challenge the fast-moving network of consumer goods organisations and academic institutions to seek a new approach to developing leadership skills.
ABSTRACT
We present a study of metal-enriched halo gas traced by Mg ii and C iv absorption at z < 2 in the MUSE Analysis of Gas around Galaxies survey and the Quasar Sightline and Galaxy Evolution ...survey. Using these large and complete galaxy surveys in quasar fields, we study the dependence of the metal distribution on galaxy properties and overdensities, out to physical projected separations of 750 kpc. We find that the cool, low-ionization gas is significantly affected by the environment across the full redshift range probed, with ≈2–3 times more prevalent and stronger Mg ii absorption in higher overdensity group environments and in regions with greater overall stellar mass and star formation rates. Complementary to these results, we have further investigated the more highly ionized gas as traced by C iv absorption, and found that it is likely to be more extended than the Mg ii gas, with ≈2 times higher covering fraction at a given distance. We find that the strength and covering fraction of C iv absorption show less significant dependence on galaxy properties and environment than the Mg ii absorption, but more massive and star-forming galaxies nevertheless also show ≈2 times higher incidence of C iv absorption. The incidence of Mg ii and C iv absorption within the virial radius shows a tentative increase with redshift, being higher by a factor of ≈1.5 and ≈4, respectively, at z > 1. It is clear from our results that environmental processes have a significant impact on the distribution of metals around galaxies and need to be fully accounted for when analysing correlations between gaseous haloes and galaxy properties.
Abstract
We investigate the effect of the accelerated expansion of the Universe due to a cosmological constant, Λ, on the cosmic star formation rate. We utilize hydrodynamical simulations from the ...eagle suite, comparing a ΛCDM (cold dark matter) Universe to an Einstein–de Sitter model with Λ = 0. Despite the differences in the rate of growth of structure, we find that dark energy, at its observed value, has negligible impact on star formation in the Universe. We study these effects beyond the present day by allowing the simulations to run forward into the future (t > 13.8 Gyr). We show that the impact of Λ becomes significant only when the Universe has already produced most of its stellar mass, only decreasing the total comoving density of stars ever formed by ${\approx }15\hbox{ per cent}$. We develop a simple analytic model for the cosmic star formation rate that captures the suppression due to a cosmological constant. The main reason for the similarity between the models is that feedback from accreting black holes dramatically reduces the cosmic star formation at late times. Interestingly, simulations without feedback from accreting black holes predict an upturn in the cosmic star formation rate for t > 15 Gyr due to the rejuvenation of massive (>1011 M⊙) galaxies. We briefly discuss the implication of the weak dependence of the cosmic star formation on Λ in the context of the anthropic principle.
Abstract
We use the hydrodynamic, cosmological EAGLE simulations to investigate how the hot gas in haloes condenses to form and grow galaxies. We select haloes from the simulations that are actively ...cooling and study the temperature, distribution and metallicity of their hot, cold and transitioning ‘cooling’ gas, placing these in the context of semi-analytic models. Our selection criteria lead us to focus on Milky Way-like haloes. We find that the hot-gas density profiles of the haloes form a progressively stronger core over time, the nature of which can be captured by a β profile that has a simple dependence on redshift. In contrast, the hot gas that will cool over a time-step is broadly consistent with a singular isothermal sphere. We find that cooling gas carries a few times the specific angular momentum of the halo and is offset in spin direction from the rest of the hot gas. The gas loses ∼60 per cent of its specific angular momentum during the cooling process, generally remaining greater than that of the halo, and it precesses to become aligned with the cold gas already in the disc. We find tentative evidence that angular-momentum losses are slightly larger when gas cools on to dispersion-supported galaxies. We show that an exponential surface density profile for gas arriving on a disc remains a reasonable approximation, but a cusp containing ∼20 per cent of the mass is always present, and disc scale radii are larger than predicted by a vanilla Fall & Efstathiou model. These scale radii are still closely correlated with the halo spin parameter, for which we suggest an updated prescription for galaxy formation models.
The existence of X-ray luminous gaseous coronae around massive disc galaxies is a long-standing prediction of galaxy formation theory in the cold dark matter cosmogony. This prediction has garnered ...little observational support, with non-detections commonplace and detections for only a relatively small number of galaxies which are much less luminous than expected. We investigate the coronal properties of a large sample of bright, disc-dominated galaxies extracted from the gimic suite of cosmological hydrodynamic simulations recently presented by Crain et al. Remarkably, the simulations reproduce the observed scalings of X-ray luminosity with K-band luminosity and star formation rate (SFR) and, when account is taken of the density structure of the halo, with disc rotation velocity as well. Most of the star formation in the simulated galaxies (which have realistic stellar mass fractions) is fuelled by gas cooling from a quasi-hydrostatic hot corona. However, these coronae are more diffuse, and of a lower luminosity, than predicted by the analytic models of White & Frenk because of a substantial increase in entropy at z∼ 1–3. Both the removal of low entropy gas by star formation and energy injection from supernovae contribute to this increase in entropy, but the latter is dominant for halo masses M200≲ 1012.5 M⊙. Only a small fraction of the mass of the hot gas is outflowing as a wind but, because of its high density and metallicity, it contributes disproportionally to the X-ray emission. The bulk of the X-ray emission, however, comes from the diffuse quasi-hydrostatic corona which supplies the fuel for ongoing star formation in discs today. Future deep X-ray observations with high spectral resolution (e.g. with NeXT/ASTRO-H or IXO) should be able to map the velocity structure of the hot gas and test this fundamental prediction of current galaxy formation theory.
Aims Little is known about the impact of ICD indication (primary vs. secondary) on health-related quality of life (HRQL). Indication may also interact with psychological factors, such as personality. ...Using a prospective design, we examined whether ICD indication and type-D personality (i.e. experiencing increased negative emotions paired with emotional non-expression) serve as modulators of HRQL at baseline and 3 months post-implantation.
Methods and results Consecutively implanted ICD patients (n = 154) completed the Type-D Scale (DS14) at baseline and the Short-Form Health Survey 36 (SF-36) at baseline and 3 months. Of all patients, 82 (53%) received an ICD due to prophylactic reasons; the prevalence of type-D was 23%. Indication had no influence on HRQL (P = 0.75). Further stratification by personality showed a main effect for type-D personality (P < 0.001), with type-D patients generally experiencing poorer HRQL; there was no main effect for indication (P = 0.45) nor was the interaction effect indication by type-D significant (P = 0.22). There was a significant improvement in HRQL over time (P = 0.001). Type-D remained an independent predictor of impaired HRQL, adjusting for clinical factors and shocks during follow-up (P < 0.001). However, in adjusted analysis there was no longer a significant change in HRQL over time (P = 0.099).
Conclusion Type-D personality but not ICD indication was associated with impaired HRQL at the time of implantation and at 3 months. In the quest for enhancing risk stratification in clinical practice, personality factors, such as type-D, should not be ignored, as both type-D and poor HRQL have been associated with increased risk of mortality in cardiac patients.
•RT-qPCR is a sensitive method for diagnosis of RVA and RVC in diarrheic suckling piglets.•Diagnostic protocols should include RVA and RVC detection.•For RVA, G-genotypes G3, G4, G5 and G9 for VP7, ...and P-genotypes P6, P7, P13 and P23 for RVC were found.•Most RVC strains possessed a G6 genotypes for VP7 and the putative P5 genotype for VP4.•Diagnostic protocols on pig farms should include assessment of bacterial virulence factors.
The importance of group A and C rotaviruses (RVA and RVC) in the pathogenesis of diarrhea in Belgian suckling pigs is poorly investigated, and it is not known which strains are circulating in the Belgian suckling pig population. Obtaining better insights in the occurrence of both viral species in the swine population is essential in order to develop accurate diagnostic, therapeutic and prophylactic strategies to protect suckling pigs against diarrhea in a durable manner.
In the present study, viral loads of RVA and RVC were quantified in diarrhea samples of suckling piglets less than 2 weeks old, collected on 36 different Belgian farms. On 22 of 36 farms tested (61%), high viral loads of RVA (6.96–11.95 log10 copies/g feces) and/or RVC (5.40–11.63 log10 copies/g feces) were detected. Seventeen RVA isolates were genotyped for their outer capsid proteins VP7 and VP4. Four different G-genotypes (G3, G4, G5 and G9) for VP7 were found together with 4 different P-genotypes (P6, P7, P13 and P23) for VP4, in 8 different G/P combinations. All characterized RVC strains belonged to genotype G6 (VP7), except for one strain possessing the G1 genotype. VP4 genes of Belgian RVC strains were genetically heterogeneous, but were classified in the genotype P5. Most rotavirus positive samples also contained Escherichia coli, whereas Clostridium perfringens infections were mainly detected in rotavirus negative samples.
Results of the present study offer better insights in the occurrence of RVA and RVC infections in Belgian diarrheic suckling piglets. As a conclusion, routine diagnostic testing for both viral species in cases of diarrhea in suckling pigs is highly recommended. Furthermore, the present findings also offer valuable information for the development of new prophylactic measures against rotavirus. Finally, the relatedness between RVC strains from pigs and other host species is described, and their possible implications in interspecies transmission events are discussed.
PDF
