Changes in left atrial deformation in hypertrophic cardiomyopathy: Evaluation by vector velocity imaging.

OBJECTIVES: Hypertrophic cardiomyopathy (HCM) represents a generalized myopathic process affecting both ventricular and atrial myocardium. We assessed the global and regional left atrial (LA) function and its relation to left ventricular (LV) mechanics and clinical status in patients with HCM using Vector Velocity Imaging (VVI). METHODS: VVI of the LA and LV was acquired from apical four- and two-chamber views of 108 HCM patients (age 40 ± 19years, 56.5% men) and 33 healthy subjects, all had normal LV systolic function. The LA subendocardium was traced to obtain atrial volumes, ejection fraction, velocities, and strain (ϵ)/strain rate (SR) measurements. RESULTS: Left atrial reservoir (ϵsys,SRsys) and conduit (early diastolic SRe) function were significantly reduced in HCM compared to controls (P  - 1.8s(- 1) was 81% sensitive and 30% specific, SRa> - 1.5s(- 1) was 73% sensitive and 40% specific. By multivariate analysis global LVϵsys and LV septal thickness are independent predictors for LAϵsys, while end systolic diameter is the only independent predictor for SRsys, P < .001. CONCLUSION: Left atrial reservoir and conduit function as measured by VVI were significantly impaired while contractile function was preserved among HCM patients. Left atrial deformation was greatly influenced by LV mechanics and correlated to severity of phenotype

Hydrodynamic Simulation of the Cosmological X-ray Background

(Abridged) We use a hydrodynamic simulation of a LambdaCDM model to predict the extragalactic X-ray background (XRB), focussing on emission from the intergalactic medium (IGM). We also include X-rays from point sources associated with galaxies in the simulation, and make maps of the angular distribution of the emission. We find that filaments in the maps are not evident, being diluted by projection. In the soft (0.5-2 keV) band, the mean intensity of radiation from intergalactic and cluster gas is 2.3*10^-12 ergdeg^-2cm^-2s^-1, 35% of the total soft band emission. This is compatible at the ~1 sigma level with estimates of the unresolved soft background from ROSAT and {\it Chandra}. Only 4% of the hard (2-10 keV) emission is associated with the IGM. Relative to AGN flux, the IGM component peaks at a lower redshift (median z~0.45) so its clustering makes an important contribution to that of the total XRB. The angular correlations on 0.1-10 arcmin scales are significant, with an amplitude roughly consistent with an extrapolation of recent ROSAT results to small scales. A cross-correlation of the XRB against nearby galaxies taken from a simulated redshift survey also yields a strong signal from the IGM. Although some recent papers have argued that the expected soft band intensity from gas in galaxy, group, and cluster halos would exceed XRB limits unless much of the gas is expelled by supernova feedback, we obtain reasonable compatibility with current observations in a simulation that incorporates cooling, star formation, and only modest feedback. A prediction of our model is that the unresolved portion of the soft XRB will remain mostly unresolved.Comment: Improved referencing of related papers. Submitted to ApJ, 19 pages, 17 postscript figures, most reduced in resolution, emulateapj.sty, for full resolution version, see http://cfa-www.harvard.edu/~rcroft/xray.ps.g

The black hole mass versus velocity dispersion relation in QSOs/Active Galactic Nuclei: observational appearance and black hole growth

Studies of massive black holes (BHs) in nearby galactic centers have revealed a tight correlation between BH mass and galactic velocity dispersion. In this paper we investigate how the BH mass versus velocity dispersion relation and the nuclear luminosity versus velocity dispersion relation in QSOs/active galactic nuclei (AGNs) are connected with the BH mass versus velocity dispersion relation in local galaxies, through the nuclear luminosity evolution of individual QSOs/AGNs and the mass growth of individual BHs. In the study we ignore the effects of BH mergers and assume that the velocity dispersion does not change significantly during and after the nuclear activity phase. Using the observed correlation in local galaxies and an assumed form of the QSO/AGN luminosity evolution and BH growth, we obtain the simulated observational appearance of the BH mass versus velocity dispersion relation in QSOs/AGNs. The simulation results illustrate how the BH accretion history (e.g., the lifetime of nuclear activity and the possibility that QSOs/AGNs accrete at a super-Eddington accretion rate at the early evolutionary stage) can be inferred from the difference between the relation in QSOs/AGNs and that in local galaxies. We also show how the difference may be weakened by the flux limit of telescopes. We expect that a large complete sample of QSOs/AGNs with accurate BH mass and velocity dispersion measurements will help to quantitatively constrain QSO/AGN luminosity evolution and BH growth models.Comment: 20 pages, including 4 figures; revised to match the published versio

Lean Maintenance Roadmap

AbstractMaintenance shares significant operating costs in an organisation. It is considered as a main pillar of the organisational performance. Lean thinking can be incorporated into maintenance activities through applying its principles and practices. Lean maintenance is a prerequisite for lean manufacturing systems. The exhaustive literature review has been conducted to collect the up-to-date maintenance strategies and activities, lean principles and practices in the lean maintenance process. The scope of this paper includes eight types of waste (non-value added maintenance activities), maintenance value stream mapping and a scheme of lean maintenance practices. The output of this paper is a proposed roadmap to apply lean thinking in a maintenance process

A framework for lean manufacturing implementation

The lean implementation initiatives can be categorised as roadmap, conceptual/implementation framework, descriptive and assessment checklist initiatives. A literature review on the lean initiatives has examined 28 initiatives. A set of rules is proposed to evaluate these initiatives with respect to nine factors impacting lean implementation. The evaluation has proved that the implementation frameworks have highest association with lean factors. However, existing lean initiatives are not demonstrated in a structured nature. The failure in managing lean implementation process is often consolidated to poor mind-set and inadequate understanding of the lean concept itself. In this paper, an attempt has been made to propose a framework to overcome some of the limitations. The proposed framework is constructed as a project-based framework with detailed four implementation phases. Appropriate practices and decision tools are proposed and assigned to each phase. However, the proposed framework is at conceptual stage. It requires further implementation to be validated.Full Tex

Enhancement of flux-line pinning in all-oxide superconductor/ferromagnet heterostructures

We have studied the local critical current density, jc, in the superconductor thin film of bilayer structures consisting of YBa2Cu3O7 and the ferromagnets La2/3Ca1/3MnO3 and SrRuO3, respectively, by means of quantitative magneto-optics. A pronounced hysteresis of jc was observed which is ascribed to the magnetization state of the ferromagnetic layer. The results are discussed within the frame of magnetic vortex - wall interactions.Comment: 9 page