258 research outputs found
Kinematics, Abundances, and Origin of Brightest Cluster Galaxies
We present kinematic parameters and absorption line strengths for three
brightest cluster galaxies, NGC 6166, NGC 6173 and NGC 6086. We find that NGC
6166 has a velocity dispersion profile which rises beyond 20 arcsec from the
nucleus, with a halo velocity dispersion in excess of 400 km/s. All three
galaxies show a positive and constant h4 Hermite moment. The rising velocity
dispersion profile in NGC 6166 thus indicates an increasing mass-to-light
ratio. Rotation is low in all three galaxies, and NGC 6173 and NGC 6086 show
possible kinematically decoupled cores. All three galaxies have Mg2 gradients
similar to those found in normal bright ellipticals, which are not steep enough
to support simple dissipative collapse models, but these could be accompanied
by dissipationless mergers which would tend to dilute the abundance gradients.
The [Mg/Fe] ratios in NGC 6166 and NGC 6086 are higher than that in NGC 6173,
and if NGC 6173 is typical of normal bright ellipticals, this suggests that cDs
cannot form from late mergers of normal galaxies.Comment: 21 pages, accepted for publication in MNRA
The color gradients of spiral disks in the Sloan Digital Sky Survey
We investigate the radial color gradients of galactic disks using a sample of
about 20,000 face-on spiral galaxies selected from the fourth data release of
the Sloan Digital Sky Survey (SDSS-DR4). We combine galaxies with similar
concentration, size and luminosity to construct composite galaxies, and then
measure their color profiles by stacking the azimuthally averaged radial color
profiles of all the member galaxies. Except for the smallest galaxies (R_{50}<3
kpc), almost all galaxies show negative disk color gradients with mean g-r
gradient G_{gr}=-0.006 mag kpc^{-1} and r-z gradient G_{rz}=-0.018 mag
kpc^{-1}. The disk color gradients are independent of the morphological types
of galaxies and strongly dependent on the disk surface brightness \mu_{d}, with
lower surface brightness galactic disks having steeper color gradients. We
quantify the intrinsic correlation between color gradients and surface
brightness as G_{gr}=-0.011\mu_{d}+0.233 and G_{rz}=-0.015\mu_{d}+0.324. These
quantified correlations provide tight observational constraints on the
formation and evolution models of spiral galaxies.Comment: 20 pages, 5 figures, Accepted for publication in RAA (Research in
Astronomy and Astrophysics
Religious revelation, secrecy and the limits of visual representation
This article seeks to contribute to a more adequate understanding of the adoption of modern audiovisual mass media by contemporary religious groups. It does so by examining Pentecostal-charismatic churches as well as the Christian mass culture instigated by its popularity, and so-called traditional religion in Ghana, which develop markedly different attitudes towards audiovisual mass media and assume different positions in the public sphere. Taking into account the complicated entanglement of traditional religion and Pentecostalism, approaching both religions from a perspective of mediation which regards media as intrinsic to religion, and seeking to avoid the pitfall of overestimating the power of modern mass media to determine the world, this article seeks to move beyond an unproductive recurrence to oppositions such as tradition and modernity, or religion and technology. It is argued that instead of taking as a point of departure more or less set ideas about the nexus of vision and modernity, the adoption of new mass media by religious groups needs to be analyzed by a detailed ethnographic investigation of how these new media transform existing practices of religious mediation. Special emphasis is placed on the tension between the possibilities of gaining public presence through new media, and the difficulty in authorizing these media, and the experiences they induce, as authentic. Copyright © 2006 SAGE Publications
Clinical outcomes of CyberKnife stereotactic body radiotherapy for peripheral stage I non-small cell lung cancer
Atomistic dynamics of sulfur-deficient high-symmetry grain boundaries in molybdenum disulfide
As a common type of structural defect, grain boundaries (GBs) play an important role in tailoring the physical and chemical properties of bulk crystals and their two-dimensional (2D) counterparts such as graphene and molybdenum disulfide (MoS2). In this study, we explore the atomic structures and dynamics of three kinds of high-symmetry GBs (α, β and γ) in monolayer MoS2. Atomic-resolution transmission electron microscopy (TEM) is used to characterize their formation and evolutionary dynamics, and atomistic simulation based analysis explains the size distribution of α-type GBs observed under TEM and the inter-GB interaction, revealing the stabilization mechanism of GBs by pre-existing sulfur vacancies. The results elucidate the correlation between the observed GB dynamics and the migration of sulfur atoms across GBs via a vacancy-mediated mechanism, offering a new perspective for GB engineering in monolayer MoS2, which may be generalized to other transition metal dichalcogenides
Display of probability densities for data from a continuous distribution
Based on cumulative distribution functions, Fourier series expansion and
Kolmogorov tests, we present a simple method to display probability densities
for data drawn from a continuous distribution. It is often more efficient than
using histograms.Comment: 5 pages, 4 figures, presented at Computer Simulation Studies XXIV,
Athens, GA, 201
WALLABY Pilot Survey:The Diversity of Ram Pressure Stripping of the Galactic H I Gas in the Hydra Cluster
This study uses HI image data from the WALLABY pilot survey with the ASKAP
telescope, covering the Hydra cluster out to 2.5. We present the
projected phase-space distribution of HI-detected galaxies in Hydra, and
identify that nearly two thirds of the galaxies within may be in
the early stages of ram pressure stripping. More than half of these may be only
weakly stripped, with the ratio of strippable HI (i.e., where the galactic
restoring force is lower than the ram pressure in the disk) mass fraction (over
total HI mass) distributed uniformly below 90%. Consequently, the HI mass is
expected to decrease by only a few 0.1 dex after the currently strippable
portion of HI in these systems has been stripped. A more detailed look at the
subset of galaxies that are spatially resolved by WALLABY observations shows
that, while it typically takes less than 200 Myr for ram pressure stripping to
remove the currently strippable portion of HI, it may take more than 600 Myr to
significantly change the total HI mass. Our results provide new clues to
understanding the different rates of HI depletion and star formation quenching
in cluster galaxies.Comment: 25 pages, 10 figures, 1 table. Accepted for publication at Ap
Sensitive and Specific Fluorescent Probes for Functional Analysis of the Three Major Types of Mammalian ABC Transporters
An underlying mechanism for multi drug resistance (MDR) is up-regulation of the transmembrane ATP-binding cassette (ABC) transporter proteins. ABC transporters also determine the general fate and effect of pharmaceutical agents in the body. The three major types of ABC transporters are MDR1 (P-gp, P-glycoprotein, ABCB1), MRP1/2 (ABCC1/2) and BCRP/MXR (ABCG2) proteins. Flow cytometry (FCM) allows determination of the functional expression levels of ABC transporters in live cells, but most dyes used as indicators (rhodamine 123, DiOC2(3), calcein-AM) have limited applicability as they do not detect all three major types of ABC transporters. Dyes with broad coverage (such as doxorubicin, daunorubicin and mitoxantrone) lack sensitivity due to overall dimness and thus may yield a significant percentage of false negative results. We describe two novel fluorescent probes that are substrates for all three common types of ABC transporters and can serve as indicators of MDR in flow cytometry assays using live cells. The probes exhibit fast internalization, favorable uptake/efflux kinetics and high sensitivity of MDR detection, as established by multidrug resistance activity factor (MAF) values and Kolmogorov-Smirnov statistical analysis. Used in combination with general or specific inhibitors of ABC transporters, both dyes readily identify functional efflux and are capable of detecting small levels of efflux as well as defining the type of multidrug resistance. The assay can be applied to the screening of putative modulators of ABC transporters, facilitating rapid, reproducible, specific and relatively simple functional detection of ABC transporter activity, and ready implementation on widely available instruments
Identification and analysis of divergent immune gene families within the Tasmanian devil genome
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