102 research outputs found

    The evolution of substructure II: linking dynamics to environment

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    We present results from a series of high-resolution N-body simulations that focus on the formation and evolution of eight dark matter halos, each of order a million particles within the virial radius. We follow the time evolution of hundreds of satellite galaxies with unprecedented time resolution, relating their physical properties to the differing halo environmental conditions. The self-consistent cosmological framework in which our analysis was undertaken allows us to explore satellite disruption within live host potentials, a natural complement to earlier work conducted within static potentials. Our host halos were chosen to sample a variety of formation histories, ages, and triaxialities; despite their obvious differences, we find striking similarities within the associated substructure populations. Namely, all satellite orbits follow nearly the same eccentricity distribution with a correlation between eccentricity and pericentre. We also find that the destruction rate of the substructure population is nearly independent of the mass, age, and triaxiality of the host halo. There are, however, subtle differences in the velocity anisotropy of the satellite distribution. We find that the local velocity bias at all radii is greater than unity for all halos and this increases as we move closer to the halo centre, where it varies from 1.1 to 1.4. For the global velocity bias we find a small but slightly positive bias, although when we restrict the global velocity bias calculation to satellites that have had at least one orbit, the bias is essentially removed.Comment: 14 pages, 14 figures, MNRAS in pres

    Arc sensitivity to cluster ellipticity, asymmetries and substructures

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    We investigate how ellipticity, asymmetries and substructures separately affect the ability of galaxy clusters to produce strong lensing events, i.e. gravitational arcs, and how they influence the arc morphologies and fluxes. This is important for those studies aiming, for example, at constraining cosmological parameters from statistical lensing, or at determining the inner structure of galaxy clusters through gravitational arcs. We do so by creating two-dimensional gradually smoothed, differently elliptical and asymmetric versions of some numerical models. On average, we find that the contributions of ellipticity, asymmetries and substructures amount to ~40%, ~10% and ~30% of the total strong lensing cross section, respectively. However, our analysis shows that substructures play a more important role in less elliptical and asymmetric clusters, even if located at large distances from the cluster centers (~1Mpc/h). Conversely, their effect is less important in highly asymmetric lenses. The morphology, position and flux of individual arcs are strongly affected by the presence of substructures in the clusters. Removing substructures on spatial scales <~50kpc/h, roughly corresponding to mass scales <~5 10^{10}M_\odot/h, alters the image multiplicity of ~35% of the sources used in the simulations and causes position shifts larger than 5'' for ~40% of the arcs longer than 5''. We conclude that any model for cluster lens cannot neglect the effects of ellipticity, asymmetries and substructures. On the other hand, the high sensitivity of gravitational arcs to deviations from regular, smooth and symmetric mass distributions suggests that strong gravitational lensing is potentially a powerfull tool to measure the level of substructures and asymmetries in clusters.Comment: 16 pages, 18 figures. Accepted version. Version with full resolution images can be found at http://www.ita.uni-heidelberg.de/~massimo/sub/publications.htm

    Home-based versus centre-based cardiac rehabilitation (Review)

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    This is the final version. Available from the Cochrane Collaboration via the DOI in this recordBACKGROUND: Cardiovascular disease is the most common cause of death globally. Traditionally, centre-based cardiac rehabilitation programmes are offered to individuals after cardiac events to aid recovery and prevent further cardiac illness. Home-based and technology-supported cardiac rehabilitation programmes have been introduced in an attempt to widen access and participation, especially during the SARS-CoV-2 pandemic. This is an update of a review previously published in 2009, 2015, and 2017. OBJECTIVES: To compare the effect of home-based (which may include digital/telehealth interventions) and supervised centre-based cardiac rehabilitation on mortality and morbidity, exercise-capacity, health-related quality of life, and modifiable cardiac risk factors in patients with heart disease SEARCH METHODS: We updated searches from the previous Cochrane Review by searching the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (Ovid), Embase (Ovid), PsycINFO (Ovid) and CINAHL (EBSCO) on 16 September 2022. We also searched two clinical trials registers as well as previous systematic reviews and reference lists of included studies. No language restrictions were applied. SELECTION CRITERIA: We included randomised controlled trials that compared centre-based cardiac rehabilitation (e.g. hospital, sports/community centre) with home-based programmes (± digital/telehealth platforms) in adults with myocardial infarction, angina, heart failure, or who had undergone revascularisation. DATA COLLECTION AND ANALYSIS: Two review authors independently screened all identified references for inclusion based on predefined inclusion criteria. Disagreements were resolved through discussion or by involving a third review author. Two authors independently extracted outcome data and study characteristics and assessed risk of bias. Certainty of evidence was assessed using GRADE. MAIN RESULTS: We included three new trials in this update, bringing a total of 24 trials that have randomised a total of 3046 participants undergoing cardiac rehabilitation. A further nine studies were identified and are awaiting classification. Manual searching of trial registers until 16 September 2022 revealed a further 14 clinical trial registrations - these are ongoing. Participants had a history of acute myocardial infarction, revascularisation, or heart failure. Although there was little evidence of high risk of bias, a number of studies provided insufficient detail to enable assessment of potential risk of bias; in particular, details of generation and concealment of random allocation sequencing and blinding of outcome assessment were poorly reported. No evidence of a difference was seen between home- and centre-based cardiac rehabilitation in our primary outcomes up to 12 months of follow-up: total mortality (risk ratio [RR] = 1.19, 95% confidence interval [CI] 0.65 to 2.16; participants = 1647; studies = 12/comparisons = 14; low-certainty evidence) or exercise capacity (standardised mean difference (SMD) = -0.10, 95% CI -0.24 to 0.04; participants = 2343; studies = 24/comparisons = 28; low-certainty evidence). The majority of evidence (N=71 / 77 comparisons of either total or domain scores) showed no significant difference in health-related quality of life up to 24 months follow-up between home- and centre-based cardiac rehabilitation. Trials were generally of short duration, with only three studies reporting outcomes beyond 12 months (exercise capacity: SMD 0.11, 95% CI -0.01 to 0.23; participants = 1074; studies = 3; moderate-certainty evidence). There was a similar level of trial completion (RR 1.03, 95% CI 0.99 to 1.08; participants = 2638; studies = 22/comparisons = 26; low-certainty evidence) between home-based and centre-based participants. The cost per patient of centre- and home-based programmes was similar. AUTHORS' CONCLUSIONS: This update supports previous conclusions that home- (± digital/telehealth platforms) and centre-based forms of cardiac rehabilitation formally supported by healthcare staff seem to be similarly effective in improving clinical and health-related quality of life outcomes in patients after myocardial infarction, or revascularisation, or with heart failure. This finding supports the continued expansion of healthcare professional supervised home-based cardiac rehabilitation programmes (± digital/telehealth platforms), especially important in the context of the ongoing global SARS-CoV-2 pandemic that has much limited patients in face-to-face access of hospital and community health services. Where settings are able to provide both supervised centre- and home-based programmes, consideration of the preference of the individual patient would seem appropriate. Although not included in the scope of this review, there is an increasing evidence base supporting the use of hybrid models that combine elements of both centre-based and home-based cardiac rehabilitation delivery. Further data are needed to determine: (1) whether the short-term effects of home/digital-telehealth and centre-based cardiac rehabilitation models of delivery can be confirmed in the longer term; (2) the relative clinical effectiveness and safety of home-based programmes for other heart patients, e.g. post-valve surgery and atrial fibrillation.National Institute for Health and Care Research (NIHR

    The evolution substructure I: a new identification method

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    We describe our new "MLAPM-halo-finder" (MHF) which is based on the adaptive grid structure of the N-body code MLAPM. We then extend the MHF code in order to track the orbital evolution of gravitationally bound objects through any given cosmological N-body simulation - our so-called "MLAPM-halo-tracker" (MHT). The mode of operation of MHT is demonstrated using a series of eight high-resolution N-body simulations of galaxy clusters. Each of these halos hosts more than one million particles within their virial radii Rvir. We use MHT as well as MHF to follow the temporal evolution of hundreds of individual satellites, and show that the radial distribution of these substructure satellites follows a "universal" radial distribution irrespective of the host halo's environment and formation history. This in fact might pose another problem for simulations of CDM structure formation as there are recent findings by Taylor et al. (2003) that the Milky Way satellites are found preferentially closer to the galactic centre and simulations underestimate the amount of central substructure, respectively. Further, this universal substructure profile is anti-biased with respect to the underlying dark matter profile. Both the halo finder MHF and the halo tracker MHT will become part of the open source MLAPM distribution.Comment: 12 pages, 10 figures, MNRAS in press, the halo finder MHF is available from http://astronomy.swin.edu.au/MLAP

    Substructures in lens galaxies: PG1115+080 and B1555+375, two fold configurations

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    We study the anomalous flux ratio which is observed in some four-image lens systems, where the source lies close to a fold caustic. In this case two of the images are close to the critical curve and their flux ratio should be equal to unity, instead in several cases the observed value differs significantly. The most plausible solution is to invoke the presence of substructures, as for instance predicted by the Cold Dark Matter scenario, located near the two images. In particular, we analyze the two fold lens systems PG1115+080 and B1555+375, for which there are not yet satisfactory models which explain the observed anomalous flux ratios. We add to a smooth lens model, which reproduces well the positions of the images but not the anomalous fluxes, one or two substructures described as singular isothermal spheres. For PG1115+080 we consider a smooth model with the influence of the group of galaxies described by a SIS and a substructure with mass 105M\sim 10^{5} M_{\odot} as well as a smooth model with an external shear and one substructure with mass 108M\sim 10^{8} M_{\odot} . For B1555+375 either a strong external shear or two substructures with mass 107M\sim 10^{7} M_{\odot} reproduce the data quite well.Comment: 26 pages, updated bibliography, Accepted for publication in Astrophysics & Space Scienc

    14-3-3ε Is Required for Germ Cell Migration in Drosophila

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    Although 14-3-3 proteins participate in multiple biological processes, isoform-specific specialized functions, as well as functional redundancy are emerging with tissue and developmental stage-specificity. Accordingly, the two 14-3-3ε proteins in Drosophila exhibit functional specificity and redundancy. Homozygotes for loss of function alleles of D14-3-3ε contain significantly fewer germ line cells (pole cells) in their gonads, a phenotype not shared by mutants in the other 14-3-3 gene leo. We show that although D14-3-3ε is enriched within pole cells it is required in mesodermal somatic gonad precursor cells which guide pole cells in their migration through the mesoderm and coalesce with them to form the embryonic gonad. Loss of D14-3-3ε results in defective pole cell migration, reduced pole cell number. We present evidence that D14-3-3ε loss results in reduction or loss of the transcription factor Zfh-1, one of the main regulatory molecules of the pole cell migration, from the somatic gonad precursor cells

    Cluster Lenses

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    Clusters of galaxies are the most recently assembled, massive, bound structures in the Universe. As predicted by General Relativity, given their masses, clusters strongly deform space-time in their vicinity. Clusters act as some of the most powerful gravitational lenses in the Universe. Light rays traversing through clusters from distant sources are hence deflected, and the resulting images of these distant objects therefore appear distorted and magnified. Lensing by clusters occurs in two regimes, each with unique observational signatures. The strong lensing regime is characterized by effects readily seen by eye, namely, the production of giant arcs, multiple-images, and arclets. The weak lensing regime is characterized by small deformations in the shapes of background galaxies only detectable statistically. Cluster lenses have been exploited successfully to address several important current questions in cosmology: (i) the study of the lens(es) - understanding cluster mass distributions and issues pertaining to cluster formation and evolution, as well as constraining the nature of dark matter; (ii) the study of the lensed objects - probing the properties of the background lensed galaxy population - which is statistically at higher redshifts and of lower intrinsic luminosity thus enabling the probing of galaxy formation at the earliest times right up to the Dark Ages; and (iii) the study of the geometry of the Universe - as the strength of lensing depends on the ratios of angular diameter distances between the lens, source and observer, lens deflections are sensitive to the value of cosmological parameters and offer a powerful geometric tool to probe Dark Energy. In this review, we present the basics of cluster lensing and provide a current status report of the field.Comment: About 120 pages - Published in Open Access at: http://www.springerlink.com/content/j183018170485723/ . arXiv admin note: text overlap with arXiv:astro-ph/0504478 and arXiv:1003.3674 by other author
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