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767 results on '"Morris, R. G."'

105. Baryons at the Edge of the X-ray Brightest Galaxy Cluster

Author

Simionescu, A., Allen, S. W., Mantz, A., Werner, N., Takei, Y., Morris, R. G., Fabian, A. C., Sanders, J. S., Nulsen, P. E. J., George, M. R., and Taylor, G. B.

Abstract

第12回宇宙科学シンポジウム (2012年1月5日-6日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)相模原キャンパス), 相模原市, 神奈川県, 12th Space Science Symposium (January 5-6, 2012. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(JAXA)(ISAS)Sagamihara Campus), Sagamihara, Kanagawa Japan, 資料番号: SA6000064058, レポート番号: P3-00G

Published
2012

106. Optical and Sunyaev–Zel'dovich observations of a new sample of distant rich galaxy clusters in the ROSAT All Sky

Author

Buddendiek, A., primary, Schrabback, T., additional, Greer, C. H., additional, Hoekstra, H., additional, Sommer, M., additional, Eifler, T., additional, Erben, T., additional, Erler, J., additional, Hicks, A. K., additional, High, F. W., additional, Hildebrandt, H., additional, Marrone, D. P., additional, Morris, R. G., additional, Muzzin, A., additional, Reiprich, T. H., additional, Schirmer, M., additional, Schneider, P., additional, and von der Linden, A., additional

Published
2015
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117. Diffusion tensor MRI correlates with executive dysfunction in patients with ischaemic leukoaraiosis.

Author

O'Sullivan M, Morris R G, Huckstep B, Jones D K, Williams S C R, Markus H S, O'Sullivan, M, Morris, R G, Huckstep, B, Jones, D K, Williams, S C R, and Markus, H S

Subjects
*ISCHEMIA, *DEMENTIA, *MAGNETIC resonance imaging, *COGNITION disorders
Abstract

Background: Cerebral small vessel disease is a common cause of vascular dementia. Both discrete lacunar infarcts and more diffuse ischaemic changes, seen as confluent high signal (leukoaraiosis) on T2 weighted magnetic resonance imaging (MRI), occur. However, there is a weak correlation between T2 lesion load and cognitive impairment. Diffusion tensor MRI (DTI) is a new technique that may provide a better index of white matter damage.Objectives: To determine whether DTI measures are correlated more strongly with cognitive performance than lesion load on T2 weighted images, and whether these correlations are independent of conventional MRI parameters.Methods: 36 patients with ischaemic leukoaraiosis (leukoaraiosis plus a previous lacunar stroke) and 19 healthy volunteers underwent DTI, conventional MRI, and neuropsychological assessment.Results: On DTI, diffusivity was increased both within lesions and in normal appearing white matter. Mean diffusivity of normal appearing white matter correlated with full scale IQ (r = -0.46, p = 0.009) and tests of executive function. These correlations remained significant after controlling for age, sex, brain volume, and T1/T2 lesion volumes. No significant correlation was identified between T2 lesion load and IQ or neuropsychological scores. Of conventional measures, brain volume correlated best with cognitive function.Conclusions: Diffusion tensor measurements correlate better with cognition than conventional MRI measures. They may be useful in monitoring disease progression and as a surrogate marker for treatment trials. The findings support the role of white matter damage and disruption of white matter connections in the pathogenesis of cognitive impairment in cerebral small vessel disease. [ABSTRACT FROM AUTHOR]

Published
2004
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124. Extreme active galactic nucleus feedback and cool-core destruction in the X-ray luminous galaxy cluster MACS J1931.8−2634

Author

Ehlert, S., primary, Allen, S. W., additional, von der Linden, A., additional, Simionescu, A., additional, Werner, N., additional, Taylor, G. B., additional, Gentile, G., additional, Ebeling, H., additional, Allen, M. T., additional, Applegate, D., additional, Dunn, R. J. H., additional, Fabian, A. C., additional, Kelly, P., additional, Million, E. T., additional, Morris, R. G., additional, Sanders, J. S., additional, and Schmidt, R. W., additional

Published
2010
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133. Leak test system

Author

Morris, R. G and Rose, A. L

Subjects
Mechanics
Abstract

System for quantitative determination of leak rates in large pressurized compartments is described. Method uses pressure reference cylinder placed in thermal contact with internal environment of compartment. Construction of equipment and details of operational procedure are reported. Illustration of equipment is included.

Published
1972

134. X-ray bright active galactic nuclei in massive galaxy clusters - III. New insights into the triggering mechanisms of cluster AGN.

Author

Ehlert, S., Allen, S. W., Brandt, W. N., Canning, R. E. A., Luo, B., Mantz, A., Morris, R. G., von der Linden, A., and Xue, Y. Q.

Subjects
ACTIVE galactic nuclei, GALACTIC redshift, GALAXY clusters, STELLAR populations, X-rays
Abstract

We present the results of a new analysis of the X-ray selected active galactic nuclei (AGN) population residing in and behind 135 of the most massive galaxy clusters in the redshift range of 0.2 < z < 0.9 observed with Chandra. With a sample of more than 11 000 X-ray point sources, we are able to measure, for the first time, evidence for evolution in the cluster AGN population beyond the expected evolution of field AGN. Our analysis shows that overall number density of cluster AGN scales with the cluster mass as ~ M500- 1.2. There is no evidence for the overall number density of cluster member X-ray AGN depending on the cluster redshift in a manner different than field AGN, nor is there any evidence that the spatial distribution of cluster AGN (given in units of the cluster overdensity radius r500) strongly depends on the cluster mass or redshift. The M-1.2 ± 0.7 scaling relation we measure is consistent with theoretical predictions of the galaxy merger rate in clusters, which is expected to scale with the cluster velocity dispersion, s, as ~s-3 or ~M-1. This consistency suggests that galaxy mergers may be an important contributor to the cluster AGN population, a result that is further corroborated by visual inspection of Hubble images for 23 spectroscopically confirmed cluster member AGN in our sample. A merger-driven scenario for the triggering of X-ray AGN is not strongly favoured by studies of field galaxies, however, suggesting that different mechanisms may be primarily responsible for the triggering of cluster and field X-ray AGN. [ABSTRACT FROM AUTHOR]

Published
2015
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