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Lineal structures in biological tissue support a wide variety of physiological functions, including membrane stabilization, vascular perfusion, and cell-to-cell communication. In 1953, Smith and Guttman demonstrated a stereological method to estimate the total length density (Lv) of linear objects based on random intersections with a two-dimensional(More)
This paper presents the design and rationale of a distributed file system for a network of more than 5000 personal computer workstations. While scale has been the dominant design influence, careful attention has also been paid to the goals of location transparency, user mobility and compatibility with existing operating system interfaces. Security is an(More)
We present a detailed analysis of the morphology, isophotal parameters and surface brightness profiles for 100 early-type members of the Virgo Cluster, from dwarfs (M B = −15.1 mag) to giants (M B = −21.8 mag). Each galaxy has been imaged in two filters, closely resembling the Sloan g and z passbands, using the Advanced Camera for Surveys on board the(More)
Imaging surveys with the Hubble Space Telescope (HST) have shown that ≈ 50–80% of low-and intermediate-luminosity galaxies contain a compact stellar nucleus at their center, regardless of host galaxy morphological type. We combine HST imaging for early-type galaxies from the ACS Virgo Cluster Survey with ground-based long-slit spectra from KPNO to show that(More)
The possibility that the Galactic spheroid was assembled from numerous, chemically-distinct proto-Galactic fragments is investigated using a Monte-Carlo technique designed to simulate the chemical evolution of the Galaxy in hierarchical formation scenarios which involve no gas dissipation. By comparing the observed and simulated metallicity distributions of(More)
The ACS Virgo Cluster Survey is a Hubble Space Telescope program to obtain high-resolution imaging, in widely separated bandpasses (F475W ≈ g and F850LP ≈ z), for 100 early-type members of the Virgo Cluster, spanning a range of ≈ 460 in blue luminosity. We use this large, homogenous dataset to examine the innermost structure of these galaxies and to(More)
We have examined the spatial distribution of substructure in clusters of galaxies using Einstein X-ray observations. Subclusters are found to have a markedly anisotropic distribution which reeects the surrounding matter distribution on supercluster scales. Our results suggest a picture in which cluster formation proceeds by mergers of sub-clusters along(More)
The ACIS instrument on board the Chandra X-ray Observatory has been used to carry out the first systematic study of low-mass X-ray binaries (LMXBs) in M87, the giant elliptical galaxy near the dynamical center of the Virgo Cluster. These images — having a total exposure time of 154 ks — are the deepest X-ray observations yet obtained of M87. We identify 174(More)
The Fornax Cluster is a conspicuous cluster of galaxies in the southern hemisphere and the second largest collection of early-type galaxies within < ∼ 20 Mpc after the Virgo Cluster. In this paper, we present a brief introduction to the ACS Fornax Cluster Survey — a program to image, in the F475W (g 475) and F850LP (z 850) bandpasses, 43 early-type galaxies(More)
We report the discovery of XMMXCS J2215.9-1738, a massive galaxy cluster at z = 1.45, which was found in the XMM Cluster Survey. The cluster candidate was initially identified as an extended X-ray source in archival XMM data. Optical spectroscopy shows that 6 galaxies within a ∼60 arcsec diameter region lie at z = 1.45 ± 0.01. Model fits to the X-ray(More)