202 research outputs found
Near Infrared Spectra and Intrinsic Luminosities of Candidate Type II Quasars at 2 < z < 3.4
We present JHK near-infrared (NIR) spectroscopy of 25 candidate Type II
quasars selected from the Sloan Digital Sky Survey, using Triplespec on the
Apache Point Observatory 3.5m telescope, FIRE at the Magellan/Baade 6.5m
telescope, and GNIRS on Gemini. At redshifts of 2 < z < 3.4, our NIR spectra
probe the rest-frame optical region of these targets, which were initially
selected to have strong lines of CIV and Ly alpha, with FWHM<2000 km/s from the
SDSS pipeline. We use the [OIII]5007 line shape as a model for the narrow line
region emission, and find that \halpha\ consistently requires a broad component
with FWHMs ranging from 1000 to 7500 km/s. Interestingly, the CIV lines also
require broad bases, but with considerably narrower widths of 1000 to 4500
km/s. Estimating the extinction using the Balmer decrement and also the
relationship in lower-z quasars between rest equivalent width and luminosity in
the [OIII] line, we find typical A_V values of 0-2 mag, which naturally explain
the attenuated CIV lines relative to Halpha. We propose that our targets are
moderately obscured quasars. We also describe one unusual object with three
distinct velocity peaks in its [OIII] spectrum.Comment: Accepted for publication in ApJ, 18 pages, 14 figure
Candidate Type II Quasars at 2 < z < 4.3 in the Sloan Digital Sky Survey III
At low redshifts, dust-obscured quasars often have strong yet narrow
permitted lines in the rest-frame optical and ultraviolet, excited by the
central active nucleus, earning the designation Type II quasars. We present a
sample of 145 candidate Type II quasars at redshifts between 2 and 4.3,
encompassing the epoch at which quasar activity peaked in the universe. These
objects, selected from the quasar sample of the Baryon Oscillation
Spectroscopic Survey of the Sloan Digital Sky Survey III, are characterized by
weak continuum in the rest-frame ultraviolet (typical continuum magnitude of i
\approx 22) and strong lines of CIV and Ly \alpha, with Full Width at Half
Maximum less than 2000 kms-1. The continuum magnitudes correspond to an
absolute magnitude of -23 or brighter at redshift 3, too bright to be due
exclusively to the host galaxies of these objects. Roughly one third of the
objects are detected in the shorter-wavelength bands of the WISE survey; the
spectral energy distributions (SEDs) of these objects appear to be intermediate
between classic Type I and Type II quasars seen at lower redshift. Five objects
are detected at rest frame 6\mu m by Spitzer, implying bolometric luminosities
of several times 10^46 erg s-1. We have obtained polarization measurements for
two objects; they are roughly 3% polarized. We suggest that these objects are
luminous quasars, with modest dust extinction (A_V ~ 0.5 mag), whose
ultraviolet continuum also includes a substantial scattering contribution.
Alternatively, the line of sight to the central engines of these objects may be
partially obscured by optically thick material.Comment: 26 pages, 13 figures, 10 tables, 4 machine readable tables. Accepted
for publication in MNRA
A Class of Topological Actions
We review definitions of generalized parallel transports in terms of
Cheeger-Simons differential characters. Integration formulae are given in terms
of Deligne-Beilinson cohomology classes. These representations of parallel
transport can be extended to situations involving distributions as is
appropriate in the context of quantized fields.Comment: 41 pages, no figure
Supernatants from lymphocytes stimulated with Bacillus Calmette-Guerin can modify the antigenicity of tumours and stimulate allogeneic T-cell responses
BACKGROUND: Reduced expression of class 1 human leucocyte antigens (HLA1) is often a mechanism by which tumours evade surveillance by the host immune system. This is often associated with an immune function that is unable to mount appropriate responses against disease, which can result in a state that favours carcinogenesis. METHODS: In the current study, we have explored the effects of Bacillus Calmette-Guerin (BCG) on the cytokine output of leucocytes, which is a key determinant in generating antitumour action, and have also assessed the effect of these cytokine cocktails on HLA1 expression in solid tumour cell lines. RESULTS: BCG potently activated a broad range of leucocytes, and also enhanced the production of cytokines that were Th(1)-predominant. Supernatants from BCG-treated leucocytes significantly increased the expression of HLA1 on the surface of cancer cell lines, which correlated with increased cytolytic T-cell activity. We also showed that the increased HLA1 expression was associated with activation of intracellular signalling pathways, which was triggered by the increases in the Th(1)-cytokines interferon-γ and tumour necrosis factor-α, as counteracting their effects negated the enhancement. CONCLUSION: These studies reaffirm the role of BCG as a putative immunotherapy through their cytokine-modifying effects on leucocytes and their capacity to enhance tumour visibility
Algebraic topological analysis of time-sequence of digital images
This paper introduces an algebraic framework for a topological analysis of time-varying 2D digital binary–valued images, each of them defined as 2D arrays of pixels. Our answer is based on an algebraic-topological coding, called AT–model, for a nD (n=2,3) digital binary-valued image I consisting simply in taking I together with an algebraic object depending on it. Considering AT–models for all the 2D digital images in a time sequence, it is possible to get an AT–model for the 3D digital image consisting in concatenating the successive 2D digital images in the sequence. If the frames are represented in a quadtree format, a similar positive result can be derived
Host galaxies of high-redshift extremely red and obscured quasars
We present Hubble Space Telescope 1.4-1.6 micron images of the hosts of ten
extremely red quasars (ERQs) and six type 2 quasar candidates at z=2-3. ERQs,
whose bolometric luminosities range between 10^47 and 10^48 erg/sec, show
spectroscopic signs of powerful ionized winds, whereas type 2 quasar candidates
are less luminous and show only mild outflows. After performing careful
subtraction of the quasar light, we clearly detect almost all host galaxies.
The median rest-frame B-band luminosity of the ERQ hosts in our sample is
10^11.2 L_Sun, or 4 L* at this redshift. Two of the ten hosts of ERQs are in
ongoing mergers. The hosts of the type 2 quasar candidates are 0.6 dex less
luminous, with 2/6 in likely ongoing mergers. Intriguingly, despite some signs
of interaction and presence of low-mass companions, our objects do not show
nearly as much major merger activity as do high-redshift radio-loud galaxies
and quasars. In the absence of an overt connection to major ongoing gas-rich
merger activity, our observations are consistent with a model in which the
near-Eddington accretion and strong feedback of ERQs are associated with
relatively late stages of mergers resulting in early-type remnants. These
results are in some tension with theoretical expectations of galaxy formation
models, in which rapid black hole growth occurs within a short time of a major
merger. Type 2 quasar candidates are less luminous, so they may instead be
powered by internal galactic processes.Comment: Accepted to MNRAS; 23 pages, including 9 figures and 2 table
On extending actions of groups
Problems of dense and closed extension of actions of compact transformation
groups are solved. The method developed in the paper is applied to problems of
extension of equivariant maps and of construction of equivariant
compactifications
Primary and malignant cholangiocytes undergo CD40 mediated Fas dependent Apoptosis, but are insensitive to direct activation with exogenous fas ligand
Introduction
Cholangiocarcinoma is a rare malignancy of the biliary tract, the incidence of which is rising, but the pathogenesis of which remains uncertain. No common genetic defects have been described but it is accepted that chronic inflammation is an important contributing factor. We have shown that primary human cholangiocyte and hepatocyte survival is tightly regulated via co-operative interactions between two tumour necrosis family (TNF) receptor family members; CD40 and Fas (CD95). Functional deficiency of CD154, the ligand for CD40, leads to a failure of clearance of biliary tract infections and a predisposition to cholangiocarcinoma implying a direct link between TNF receptor-mediated apoptosis and the development of cholangiocarcinoma.
Aims
To determine whether malignant cholangiocytes display defects in CD40 mediated apoptosis. By comparing CD40 and Fas-mediated apoptosis and intracellular signalling in primary human cholangiocytes and three cholangiocyte cell lines.
Results
Primary cholangiocytes and cholangiocyte cell lines were relatively insensitive to direct Fas-mediated killing with exogenous FasL when compared with Jurkat cells, which readily underwent Fas-mediated apoptosis, but were extremely sensitive to CD154 stimulation. The sensitivity of cells to CD40 activation was similar in magnitude in both primary and malignant cells and was STAT-3 and AP-1 dependent in both.
Conclusions
1) Both primary and malignant cholangiocytes are relatively resistant to Fas–mediated killing but show exquisite sensitivity to CD154, suggesting that the CD40 pathway is intact and fully functional in both primary and malignant cholangiocytes 2) The relative insensitivity of cholangiocytes to Fas activation demonstrates the importance of CD40 augmentation of Fas dependent death in these cells. Agonistic therapies which target CD40 and associated intracellular signalling pathways may be effective in promoting apoptosis of malignant cholangiocytes
(Quantum) Space-Time as a Statistical Geometry of Fuzzy Lumps and the Connection with Random Metric Spaces
We develop a kind of pregeometry consisting of a web of overlapping fuzzy
lumps which interact with each other. The individual lumps are understood as
certain closely entangled subgraphs (cliques) in a dynamically evolving network
which, in a certain approximation, can be visualized as a time-dependent random
graph. This strand of ideas is merged with another one, deriving from ideas,
developed some time ago by Menger et al, that is, the concept of probabilistic-
or random metric spaces, representing a natural extension of the metrical
continuum into a more microscopic regime. It is our general goal to find a
better adapted geometric environment for the description of microphysics. In
this sense one may it also view as a dynamical randomisation of the causal-set
framework developed by e.g. Sorkin et al. In doing this we incorporate, as a
perhaps new aspect, various concepts from fuzzy set theory.Comment: 25 pages, Latex, no figures, some references added, some minor
changes added relating to previous wor
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