5,023 research outputs found
Overexpression of HER2 modulates bcl-2, bcl-XL, and tamoxifen-induced apoptosis in human MCF-7 breast cancer cells
Overexpression of HER2 in estrogen receptor (ER)-positive human breast tumors has been associated with resistance to endocrine therapy. Here we investigated the effects of HER2 on expression of apoptotic pathways and modulation of tamoxifen-induced apoptosis in ER-positive MCF-7 breast cancer cells. We report that HER2 overexpression in MCF-7 cells is accompanied by up-regulation of antiapoptotic Bcl-2 and Bcl-XL proteins and suppression of tamoxifen-induced apoptosis. In addition, human tumor cell lines that are both ER positive and overexpress HER2 also express enhanced levels of Bcl-2 compared to cells that are either ER positive or overexpress HER2 alone. Our findings suggest that possible deregulation of antiapoptotic Bcl-2 and Bcl-XL may be associated with the enhanced survival of HER2-overexpressing and ER-positive breast cancer cells treated with antiestrogens
Far infrared observations of pre-protostellar sources in Lynds 183
Using ISOPHOT maps at 100 and 200um and raster scans at 100, 120, 150 and
200um we have detected four unresolved far-infrared sources in the high
latitude molecular cloud L183. Two of the sources are identified with 1.3mm
continuum sources found by Ward-Thompson et al. and are located near the
temperature minimum and the coincident column density maximum of dust
distribution. For these two sources, the ISO observations have enabled us to
derive temperatures (about 8.3 K) and masses (about 1.4 and 2.4 solar masses).
They are found to have masses greater than or comparable to their virial masses
and are thus expected to undergo gravitational collapse. We classify them as
pre-protostellar sources. The two new sources are good candidates for
pre-protostellar sources or protostars within L183.Comment: 12 pages, 7 Postscript figures, 1 JPEG figure. Accepted for
publication in Astronomy & Astrophysic
SCUBA and Spitzer observations of the Taurus molecular cloud - pulling the bull's tail
We present continuum data from the Submillimetre Common-User Bolometer Array
(SCUBA) on the James Clerk Maxwell Telescope (JCMT), and the Mid-Infrared
Photometer for Spitzer (MIPS) on the Spitzer Space Telescope, at submillimetre
and infrared wavelengths respectively. We study the Taurus molecular cloud 1
(TMC1), and in particular the region of the Taurus Molecular Ring (TMR). In the
continuum data we see no real evidence for a ring, but rather we see one side
of it only, appearing as a filament. We name the filament `the bull's tail'.
The filament is seen in emission at 850, 450 and 160um, and in absorption at
70um. We compare the data with archive data from the Infra-Red Astronomical
Satellite (IRAS) at 12, 25, 60, 100um, in which the filament is also seen in
absorption. We find that the emission from the filament consists of two
components: a narrow, cold (~8K), central core; and a broader, slightly warmer
(~12K), shoulder of emission. We use a radiative transfer code to model the
filament's appearance, either in emission or absorption, simultaneously at each
of the different wavelengths. Our best fit model uses a Plummer-like density
profile and a homogeneous interstellar dust grain population. Unlike previous
work on a similar, but different filament in Taurus, we require no grain
coagulation to explain our data.Comment: 10 pages, 9 Figures, Accepted by MNRA
The initial conditions of isolated star formation - VI. SCUBA mapping of prestellar cores
Observations have been carried out with SCUBA at the JCMT of 52 molecular
cloud cores that do not contain any sign of protostellar activity. These are
all therefore candidate prestellar cores, which are believed to represent the
stage of star formation that precedes the formation of a protostar. 29 of the
52 cores were detected at 850 microns at varying levels of signal-to-noise
ratio greater than 3 sigma at peak. The detected cores were split into 'bright'
cores and `intermediate' cores, depending on their peak flux density at 850
microns. Cores with peak 850 microns flux densities greater than 170 mJy/beam
were designated 'bright' (13 cores), while those flux densities below this
value were designated 'intermediate' (16 cores). This dividing line corresponds
to A_v~50 under typical assumptions. The data are combined with our previously
published ISO data, and the physical parameters of the cores, such as density
and temperature, are calculated. Detailed fitting of the bright core radial
profiles shows that they are not critical Bonnor-Ebert spheres, in agreement
with previous findings. However, we find that intermediate cores, such as B68
(which has previously been claimed to be a Bonnor-Ebert sphere), may in fact be
consistent with the Bonnor-Ebert criterion, suggesting perhaps that cores pass
through such a phase during their evolution. We make rough estimates of core
lifetimes based on the statistics of detections and find that the lifetime of a
prestellar core is roughly ~3x10^5 years, while that of a bright core is
\~1.5x10^5 years. Comparisons with some magnetic and turbulence regulated
collapse models show that no model can match all of the data. Models that are
tuned to fit the total prestellar core lifetime, do not predict the relative
numbers of cores seen at each stage.Comment: 23 pages, 52 figures, accepted by MNRAS, alternate PDF w/all figures
available from
http://www.astro.cf.ac.uk/pub/Derek.Ward-Thompson/publications.htm
Mathieu twining characters for K3
The analogue of the McKay-Thompson series for the proposed Mathieu group
action on the elliptic genus of K3 is analysed. The corresponding NS-sector
twining characters have good modular properties and satisfy remarkable
replication identities. These observations provide strong support for the
conjecture that the elliptic genus of K3 carries indeed an action of the
Mathieu group M24.Comment: 19 page
E.P. Thompson and cultural sociology: questions of poetics, capitalism and the commons
There is currently a need for cultural sociology to readdress the work of humanistic and cultural Marxism. While more recently much of this work has been dismissed the appearance of more radical social movements and the on-going crisis of neoliberalism suggests that it still has much to tell us. In this respect, this article seeks to readdress the writing of historian E.P.Thompson arguing that his work on the class based and other social movements, poetics, critique of positivism and economic reason, utopia and work on the idea of the commons all has much to offer more contemporary scholarship. While the article recognises that the cultural Marxism of figures like Thompson can-not simply be resurrected it does continue to offer a number of critical insights lacking from other traditions within cultural sociology. By readdressing the internal complexity of Thompson’s writing the argumentative strategy of this article suggests that cultural sociology needs to move beyond more simplistic understandings of cultural Marxism and more carefully explore what it has to offer
On the reliability of polarization estimation using Rotation Measure Synthesis
We benchmark the reliability of the Rotation Measure (RM) synthesis algorithm
using the 1005 Centaurus A field sources of Feain et al. (2009). The RM
synthesis solutions are compared with estimates of the polarization parameters
using traditional methods. This analysis provides verification of the
reliability of RM synthesis estimates. We show that estimates of the
polarization parameters can be made at lower S/N if the range of RMs is
bounded, but reliable estimates of individual sources with unusual RMs require
unconstrainted solutions and higher S/N.
We derive from first principles the statistical properties of the
polarization amplitude associated with RM synthesis in the presence of noise.
The amplitude distribution depends explicitly on the amplitude of the
underlying (intrinsic) polarization signal. Hence it is necessary to model the
underlying polarization signal distribution in order to estimate the
reliability and errors in polarization parameter estimates. We introduce a
Bayesian method to derive the distribution of intrinsic amplitudes based on the
distribution of measured amplitudes.
The theoretically-derived distribution is compared with the empirical data to
provide quantitative estimates of the probability that an RM synthesis solution
is correct as a function of S/N. We provide quantitative estimates of the
probability that any given RM synthesis solution is correct as a function of
measured polarized amplitude and the intrinsic polarization amplitude compared
to the noise.Comment: accepted for publication in the Astrophysical Journa
Inner Structure of Protostellar Collapse Candidate B335 Derived from Millimeter-Wave Interferometry
We present a study of the density structure of the protostellar collapse
candidate B335 using continuum observations from the IRAM Plateau de Bure
Interferometer made at wavelengths of 1.2mm and 3.0mm. We analyze these data,
which probe spatial scales from 5000 AU to 500 AU, directly in the visibility
domain by comparison to synthetic observations constructed from models that
assume different physical conditions. This approach allows for much more
stringent constraints to be derived from the data than from analysis of images.
A single radial power law in density provides a good description of the data,
with best fit power law index p=1.65+/-0.05. Through simulations, we quantify
the sensitivity of this result to various model uncertainties, including
assumptions of temperature distribution, outer boundary, dust opacity spectral
index, and an unresolved central component. The largest uncertainty comes from
the unknown presence of a centralized point source. A point source with 1.2mm
flux of F=12+/-7 mJy reduces the density index to p=1.47+/-0.07. The remaining
sources of systematic uncertainty, the most important of which is the
temperature distribution, likely contribute a total uncertainty of < 0.2. We
therefore find strong evidence that the power law index of the density
distribution within 5000 AU is significantly less than the value at larger
radii, close to 2.0 from previous studies of dust emission and extinction.
These results conform well to the generic paradigm of isolated, low-mass star
formation which predicts a power law density index close to p=1.5 for an inner
region of gravitational free fall onto the protostar.Comment: Accepted to the Astrophysical Journal; 27 pages, 3 figure
Discovery of Isotopes of the Transuranium Elements with 93 <= Z <= 98
One hundred and five isotopes of the transuranium elements neptunium,
plutonium, americium, curium, berkelium and californium have so far been
observed; the discovery of these isotopes is discussed. For each isotope a
brief summary of the first refereed publication, including the production and
identification method, is presented.Comment: To be published in Atomic Data and Nuclear Data Table
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