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It has traditionally been accepted that quasars and strong emission-line radio galaxies, although situated in regions of enhanced galaxy density, are rarely found within rich clusters (Yee and Green 1984; Longair and Seldner 1978). The recent finding by Yee and Green (1987) that at z ≳0.5 a substantial fraction of optically bright radio-loud quasars are found in galaxy clusters as rich as Abell class 1, suggests that a substantial evolution of the environments of rich clusters has taken place over this short time period. Similar results for radio galaxies have also been obtained by Hill and Lilly (1988, private communication). If this is an evolutionary effect, then at least some first-rank elliptical galaxies in low-redshift rich clusters must contain remnants of active galactic nuclei (AGN). Motivated by this, we attempted to find traces of AGN-like activity in a sample of FR class I radio galaxies which are known to be “quiescent” absorption-line systems situated in low-redshift clusters.
Quasars at redshifts < 1.0 provide good markers for discovering galaxies and galaxy clusters at moderately high redshifts. Recent results from a comprehensive program of imaging surveys of galaxies in quasar fields are summarized.
Strategies for the involvement of primary care in the management of patients with presumed or diagnosed dementia are heterogeneous across Europe. We wanted to explore attitudes of primary care physicians (PCPs) when managing dementia: (i) the most popular cognitive tests, (ii) who had the right to initiate or continue cholinesterase inhibitor or memantine treatment, and (iii) the relationship between the permissiveness of these rules/guidelines and PCP's approach in the dementia investigations and assessment.
Key informant survey. Setting: Primary care practices across 25 European countries. Subjects: Four hundred forty-five PCPs responded to a self-administered questionnaire. Two-step cluster analysis was performed using characteristics of the informants and the responses to the survey. Main outcome measures: Two by two contingency tables with odds ratios and 95% confidence intervals were used to assess the association between categorical variables. A multinomial logistic regression model was used to assess the association of multiple variables (age class, gender, and perceived prescription rules) with the PCPs’ attitude of “trying to establish a diagnosis of dementia on their own.”
Discrepancies between rules/guidelines and attitudes to dementia management was found in many countries. There was a strong association between the authorization to prescribe dementia drugs and pursuing dementia diagnostic work-up (odds ratio, 3.45; 95% CI 2.28–5.23).
Differing regulations about who does what in dementia management seemed to affect PCP's engagement in dementia investigations and assessment. PCPs who were allowed to prescribe dementia drugs also claimed higher engagement in dementia work-up than PCPs who were not allowed to prescribe.
CCD images of quasars having redshifts between 0.3 and 0.65 are analyzed to study the association of galaxies with quasars. Average luminosity functions (LF) of the excess galaxies associated with the radio-loud quasars are determined. It is found that for the sub-sample with z>0.55, there is a significant brightening of the characteristic magnitude M*, if qo is assumed to be 0. Comparing computed quasar-galaxy spatial-covariance amplitudes, we can conclude, at the 0.025 significance level, that the spatial-covariance amplitudes of the sub-sample with z>0.55 are greater than those of the lower redshift quasars. This indicates that there has been a strong evolution of preferred sites for bright radio-loud quasars, implying some number-density evolution of quasars has taken place, and that some rich clusters at z∼0.6, in comparison with the local rich clusters, have significantly different physical conditions.
A recent comprehensive photometric survey of 45 low-z X-ray selected Abell clusters (López-Cruz 1997) has measured significant variations in the faint end slope of the luminosity function (LF). This result indicates that dwarf galaxies (dGs) comprise a different fraction of the cluster population as a function cluster environment. Clusters having a central “cD-like” galaxy have a flatter faint end slope than non-cD clusters. Also, cD clusters were found to have a dwarf-to-giant ratio (D/ G) which was smaller than non-cD clusters. López-Cruz et al. (1997) has suggested that the light contained in cD envelopes can be accounted for by assuming that it is produced from stars that originally formed dGs. In this simple model, the D/ G would be expected to increase with radial distance from the cluster centre due to the decrease in the disruptive forces.
We report on the first measurement of the average mass and mass-to-light ratio of galaxy groups by analysing the weak lensing signal induced by these systems. The Canadian Network for Observational Cosmology Field Galaxy Redshift Survey (CNOC2) allows the identification of a large number of groups at intermediate redshifts. For our analysis we use a sample of 50 groups which are selected on the basis of a careful dynamical analysis of group candidates. We detect a signal at the 99% confidence limit. The best fit singular isothermal sphere model yields an Einstein radius rE = 0″.72 ± 0″.29. This corresponds to a velocity dispersion of 〈σ2〉1/2 = 274±+48-59 km/s, which is in good agreement with the dynamical estimate. Under the assumption that the light traces the mass, we find an average mass-to-light ratio of 191 ± 83 h in the restframe B band. Unlike dynamical estimates, this result is insensitive to problems associated with determining group membership. We use the observed mass-to-light ratio to estimate the matter density of the universe, for which we find Ωm = 0.19 ± 0.10 (ΩΛ = 0), in good agreement with other recent estimates. For a closed universe (Ωm + ΩΛ = 1), we obtain Ωm = 0.13 ± 0.07.
The Red-Sequence Cluster Survey (RCS) is a 100 deg2 optical survey for high-redshift galaxy clusters. One of the goals of the survey is a measurement of Ωm and σ8 via the evolution of the mass spectrum of galaxy clusters. Herein we briefly describe how this will initially be done, and also demonstrate the eventual power of the RCS for this type of measurement by a qualitative analysis of the first 1/10th of the survey data.
We have carried out a number of imaging surveys of fields around quasars to study their global environments (e.g. Yee and Green 1987, Ellingson, Yee and Green 1991). The richness of the galaxy cluster environment of each quasar was determined using the galaxy-quasar spatial covariance amplitude, a quantity which is normalized for the expected luminosity and spatial distribution of galaxies (Longair and Seldner 1978, Yee and Green 1987). We find that ~40% of the brightest radio-loud quasars inhabit rich clusters of galaxies (Abell class 1 or higher) at z≳0.5 whereas only fainter AGN inhabit clusters at more recent epochs (Figure 1). This can be understood if quasars in rich clusters evolve much faster than those in poor environments.
Simulation of turbulent flows with shocks employing subgrid-scale (SGS) filtering may encounter a loss of accuracy in the vicinity of a shock. This paper addresses the accuracy improvement of LES of turbulent flows in two ways: (a) from the SGS model standpoint and (b) from the numerical method improvement standpoint. In an internal report, Kotov et al. ( “High Order Numerical Methods for large eddy simulation (LES) of Turbulent Flows with Shocks”, CTR Tech Brief, Oct. 2014, Stanford University), we performed a preliminary comparative study of different approaches to reduce the loss of accuracy within the framework of the dynamic Germano SGS model. The high order low dissipative method of Yee & Sjögreen (2009) using local flow sensors to control the amount of numerical dissipation where needed is used for the LES simulation. The considered improved dynamics model approaches include applying the one-sided SGS test filter of Sagaut & Germano (2005) and/or disabling the SGS terms at the shock location. For Mach 1.5 and 3 canonical shock-turbulence interaction problems, both of these approaches show a similar accuracy improvement to that of the full use of the SGS terms. The present study focuses on a five levels of grid refinement study to obtain the reference direct numerical simulation (DNS) solution for additional LES SGS comparison and approaches. One of the numerical accuracy improvements included here applies Harten's subcell resolution procedure to locate and sharpen the shock, and uses a one-sided test filter at the grid points adjacent to the exact shock location.
We present the first measurement of the evolution of the apparent projected shape of galaxy clusters from 0.2≲ z≲2. We measure the ellipticities (εcl) of homogeneously selected galaxy clusters over this wide redshift range. We confirm the predictions of N-body simulations that clusters are more elongated at higher redshift, finding the mean projected ellipticity changes linearly from 0.36±0.01 to 0.25±0.01 over that range. The fraction of relaxed clusters (defined as having εcl<0.2) is 9+5-3% at z∼1.8, steadily increasing to 42+7-6% by z∼0.3. Because more spherical clusters have a higher degree of virialization, our result shows significant evolution in the degree of cluster virialization over cosmic time.
A study of 7,388 consecutive patients after hepatic resection between 2011 and 2012 identified hepatolithiasis, cirrhosis, and intraoperative blood transfusion as the only independent risk factors of both incisional and organ/space surgical site infection (SSI). Patients with these conditions should be cared for with caution to lower SSI rates.
In July 2011, a cluster of Yersinia enterocolitica infections was detected in southwestern Pennsylvania, USA. We investigated the outbreak's source and scope in order to prevent further transmission. Twenty-two persons were diagnosed with yersiniosis; 16 of whom reported consuming pasteurized dairy products from dairy A. Pasteurized milk and food samples were collected from this dairy. Y. enterocolitica was isolated from two products. Isolates from both food samples and available clinical isolates from nine dairy A consumers were indistinguishable by pulsed-field gel electrophoresis. Environmental and microbiological investigations were performed at dairy A and pasteurization deficiencies were noted. Because consumption of pasteurized milk is common and outbreaks have the potential to become large, public health interventions such as consumer advisories or closure of the dairy must be implemented quickly to prevent additional cases if epidemiological or laboratory evidence implicates pasteurized milk as the outbreak source.
The variable high-order multiblock overlapping (overset) grids method of Sjögreen & Yee [CiCP, Vol. 5, 2009] for a perfect gas has been extended to nonequilibrium flows. This work makes use of the recently developed high-order well-balanced shock-capturing schemes and their filter counterparts [Wang et al., J. Comput. Phys., 2009, 2010] that exactly preserve certain non-trivial steady state solutions of the chemical nonequilibrium governing equations. Multiscale turbulence with strong shocks and flows containing both steady and unsteady components is best treated by mixing of numerical methods and switching on the appropriate scheme in the appropriate subdomains of the flow fields, even under the multiblock grid or adaptive grid refinement framework. While low dissipative sixth- or higher-order shock-capturing filter methods are appropriate for unsteady turbulence with shocklets, second- and third- order shock-capturing methods are more effective for strong steady or nearly steady shocks in terms of convergence. It is anticipated that our variable high-order overset grid framework capability with its highly modular design will allow for an optimum synthesis of these new algorithms in such a way that the most appropriate spatial discretizations can be tailored for each particular region of the flow. In this paper some of the latest developments in single block high-order filter schemes for chemical nonequilibrium flows are applied to overset grid geometries. The numerical approach is validated on a number of test cases characterized by hypersonic conditions with strong shocks, including the reentry flow surrounding a 3D Apollo-like NASA Crew Exploration Vehicle that might contain mixed steady and unsteady components, depending on the flow conditions.
XANES (X-ray Absorption Near Edge Spectroscopy) has been employed to evaluate the efficacy of a process designed to encapsulate and reduce TcO4- in cement matrices, thereby immobilizing Tc. The oxidation state of Se following bioremediation of Se by bacteria has also been determined by XANES. The XANES measurements were performed at the Stanford Synchrotron Radiation Laboratory (SSRL) and the National Synchrotron Light Source (NSLS) at the respective K edges of Tc (21.0 keV) and Se (12.7 keV). Comparison of the XANES spectra of Tc in untreated cement to Tc in slag treated cement and to the chemical shifts of reference materials, shows that the oxidation state of Tc is the same in both cements. Thus, the addition of a reducing agent to the cement formulation does not significantly reduce the TcO4-. The common soil bacterium, Bacillus subtilis, is known to incorporate Se on or within the cell wall when exposed to a Se(IV) solution. The Se XANES spectra of B. subtilis, as well as bacillus isolated from selenium rich soil, show that the organisms reduce selenite to the red allotrope of elemental Se.
The competitive adsorption of lung surfactant (LS) and albumin at the air-liquid interface and the ability of polyethylene glycol (PEG) to mediate LS adsorption are analyzed using pressure area isotherms and grazing incidence x-ray diffraction (GIXD). The addition of albumin drastically reduces the amount of LS on the interface and slightly increases the LS lattice spacing. The addition of PEG restores the characteristic LS peaks, yielding a slightly more compact lattice. The scattering results are consistent with recent work which proposed that albumin creates a physical barrier which eliminates LS adsorption and that PEG enhances LS adsorption but does not significantly change LS surface ordering.
We use deep nIR imaging of 15 galaxy clusters at z ≃ 1 to study the build-up of the red-sequence in rich clusters since the Universe was half its present age. We measured, for the first time, the luminous-to-faint ratio of red-sequence galaxies at z=1 from a large ensemble of clusters, and found an increase of 100% in the ratio of luminous-to-faint red-sequence galaxies from z=0.45 to 1.0. The measured change in this ratio as function of redshift is well-reproduced by a simple evolutionary model developed in this work, that consists in an early truncation of the star formation for bright cluster galaxies and a delayed truncation for faint cluster galaxies.
The adaptive nonlinear filtering approach for shock/turbulence gas dynamics and magnetohydrodynamics (MHD) flows adopted in our previous work is employed in conjunction with compact high-order methods as the spatial base scheme. The objective is to compare the performance of nonlinear filtering in compact high-order schemes with nonlinear filtering in standard central (non-compact) schemes for multiscale problems containing shock waves.