1,346 research outputs found
A Role for the PPARγ in Cancer Therapy
In 1997, the first published reports highlighted PPARγ
as a novel cancer therapeutic target regulating differentiation of cancer cells. A subsequent flurry of papers described these activities more widely and fuelled further enthusiasm for differentiation therapy, as the ligands for the PPARγ were seen as well tolerated and in several cases well-established in other therapeutic contexts.
This initial enthusiasm and promise was somewhat tempered by contradictory findings in several murine cancer models and equivocal trial findings. As more understanding has emerged in recent years, a renaissance has occurred in targeting PPARγ within the context of either chemoprevention or chemotherapy.
This clarity has arisen in part through a clearer understanding of PPARγ biology, how the receptor interacts with other proteins and signaling events, and the mechanisms that modulate its transcriptional actions. Equally greater translational understanding of this target has arisen from a clearer understanding of in vivo murine cancer models. Clinical exploitation will most likely require precise and quantifiable description of PPARγ actions, and resolution of which targets are the most beneficial to target combined with an understanding of the mechanisms that limits its anticancer effectiveness
Catalog of Galaxy Morphology in Four Rich Clusters: Luminosity Evolution of Disk Galaxies at 0.33<z<0.83
Hubble Space Telescope (HST) imaging of four rich, X-ray luminous, galaxy
clusters (0.33<z<0.83) is used to produce quantitative morphological
measurements for galaxies in their fields. Catalogs of these measurements are
presented for 1642 galaxies brighter than F814W(AB)=23.0 . Galaxy luminosity
profiles are fitted with three models: exponential disk, de Vaucouleurs bulge,
and a disk-plus-bulge hybrid model. The best fit is selected and produces a
quantitative assessment of the morphology of each galaxy: the principal
parameters derived being B/T, the ratio of bulge to total luminosity, the scale
lengths and half-light radii, axial ratios, position angles and surface
brightnesses of each component. Cluster membership is determined using a
statistical correction for field galaxy contamination, and a mass normalization
factor (mass within boundaries of the observed fields) is derived for each
cluster. In the present paper, this catalog of measurements is used to
investigate the luminosity evolution of disk galaxies in the rich-cluster
environment. Examination of the relations between disk scale-length and central
surface brightness suggests, under the assumption that these clusters represent
a family who share a common evolutionary history and are simply observed at
different ages, that there is a dramatic change in the properties of the small
disks (h < 2 kpc). This change is best characterized as a change in surface
brightness by about 1.5 magnitude between z=0.3 and z=0.8 with brighter disks
at higher redshifts.Comment: 53 pages, including 13 figures and 7 tables. Accepted for publication
in the Astrophysical Journal Supplement Serie
Evolution of galactic disks in clusters and the field at in the CNOC survey
Two-dimensional surface photometry is presented for a sample of 351 late-type
galaxies with . These objects are drawn from the Canadian
Network for Observational Cosmology (CNOC) cluster survey and are either
spectroscopically confirmed members of clusters at (64 galaxies),
(45), and (36) or field galaxies with similar redshifts. Galaxies
in the rich cluster Abell 2256 at were also analyzed with the same
methods to provide a local reference point. At redshifts of (0.23, 0.43, 0.55)
the disk surface brightness in cluster late-type galaxies is higher in the
-band by )
mag, respectively, relative to the Freeman (1970) constant surface-brightness
relation; whereas disks in cluster galaxies at are consistent with
that relation. Field galaxies show a progressive disk-brightening with redshift
that is consistent with that seen in the cluster population. Taken together
with similar measurements of early-type galaxies (Schade et al. 1996a), these
results suggest that the evolution of the field and cluster galaxy populations
are similar, although we emphasize that our sample of cluster galaxies is
dominated by objects at large distances (up to 3 Mpc) from the dense cluster
core, so that the implications of these findings with respect to the
Butcher-Oemler effect and the morphology-density relation will not be clear
until an analysis of galaxy properties as a function of cluster-centric
distance is completed.Comment: accepted for ApJ Letters, also available at
http://manaslu.astro.utoronto.ca/~carlberg/cnoc/disk
The Luminosity Function of Field Galaxies in the CNOC1 Redshift Survey
We have computed the luminosity function for 389 field galaxies from the
Canadian Network for Observational Cosmology cluster redshift survey (CNOC1),
over redshifts z = 0.2-0.6. We find Schechter parameters M^* - 5 log h = -19.6
\pm 0.3 and \alpha = -0.9 \pm 0.2 in rest-frame B_{AB}. We have also split our
sample at the color of a redshifted but nonevolving Sbc galaxy, and find
distinctly different luminosity functions for red and blue galaxies. Red
galaxies have a shallow slope \alpha \approx -0.4 and dominate the bright end
of the luminosity function, while blue galaxies have a steep \alpha \approx
-1.4 and prevail at the faint end. Comparisons of the CNOC1 results to those
from the Canada-France (CFRS) and Autofib redshift surveys show broad agreement
among these independent samples, but there are also significant differences
which will require larger samples to resolve. Also, in CNOC1 the red galaxy
luminosity density stays about the same over the range z = 0.2-0.6, while the
blue galaxy luminosity density increases steadily with redshift. These results
are consistent with the trend of the luminosity density vs. redshift relations
seen in the CFRS, though the normalizations of the luminosity densities appear
to differ for blue galaxies. Comparison to the local luminosity function from
the Las Campanas redshift survey (LCRS) shows that the luminosity density at z
\approx 0.1 is only about half that seen at z \approx 0.4. A change in the
luminosity function shape, particularly at the faint end, appears to be
required to match the CNOC1 and LCRS luminosity functions, if galaxy evolution
is the sole cause of the differences seen. However, it should be noted that the
specific details of the construction of different surveys may complicate the
comparison of results and so may need to be considered carefully.Comment: 22 pages, including 6 postscript figures, uses AASTEX v4.0 style
files. Corrected minor typos and updated references. Results and conclusions
unchanged. Final version to appear in the Astrophysical Journa
Virial mass in DGP brane cosmology
We study the virial mass discrepancy in the context of a DPG brane-world
scenario and show that such a framework can offer viable explanations to
account for the mass discrepancy problem. This is done by defining a
geometrical mass that we prove to be proportional to the virial
mass. Estimating using observational data, we show that it
behaves linearly with and has a value of the order of , pointing
to a possible resolution of the virial mass discrepancy. We also obtain the
radial velocity dispersion of galaxy clusters and show that it is compatible
with the radial velocity dispersion profile of such clusters. This velocity
dispersion profile can be used to differentiate various models predicting the
virial mass.Comment: 12 pages, 1 figure, to appear in CQ
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