132,320 research outputs found
Self-consistent Gravitational Lens Reconstruction
We present a new method for directly determining accurate, self-consistent
cluster lens mass and shear maps in the strong lensing regime from the
magnification bias of background galaxies. The method relies upon pixellisation
of the surface mass density distribution which allows us to write down a
simple, solvable set of equations. We also show how pixellisation can be
applied to methods of mass determination from measurements of shear and present
a simplified method of application. The method is demonstrated with cluster
models and applied to magnification data from the lensing cluster Abell 1689.Comment: 5 pages, 4 figures. References added to introduction. Accepted by
MNRA
Nonlinear Cosmological Power Spectra in Real and Redshift--Space
We present an expression for the nonlinear evolution of the cosmological
power spectrum based on following Lagrangian trajectories. This is simplified
using the Zel'dovich approximation to trace particle displacements, assuming
Gaussian initial conditions. The model is found to exhibit the transfer of
power from large to small scales expected in self- gravitating fields. We have
extended this analysis into redshift-space and found a solution for the
nonlinear, anisotropic redshift-space power spectrum in the limit of
plane--parallel redshift distortions. The quadrupole-to- monopole ratio is
calculated for the case of power-law initial spectra. We find that the shape of
this ratio depends on the shape of the initial spectrum, but when scaled to
linear theory depends only weakly on the redshift-space distortion parameter,
. The point of zero-crossing of the quadrupole, , is found to obey
a scaling relation. This model is found to be in agreement with -body
simulations on scales down to the zero-crossing of the quadrupole, although the
wavenumber at zero-crossing is underestimated. These results are applied to the
quadrupole--monopole ratio found in the merged QDOT+1.2 Jy IRAS redshift
survey. We have estimated that the distortion parameter is constrained to be
at the level. The local primordial spectral slope is not
well constrained, but analysis suggests in the translinear
regime. The zero-crossing scale of the quadrupole is
and from this we infer the amplitude of clustering is .
We suggest that the success of this model is due to nonlinear redshift--space
effects arising from infall onto caustics and is not dominated by virialised
cluster cores.Comment: 13 pages, uufiles, Latex with 6 postscript figures, submitted to
MNRA
Topical prostaglandin analogues and conjunctival inflammation in uveitic glaucoma.
A pilot study to determine whether topical prostaglandin analogues alter the expression of conjunctival inflammatory markers in patients with uveitic glaucoma.Prospective, single-masked case series of 20 patients with uveitis and secondary raised intraocular pressure. Participants were divided into four groups of five patients dependent on their use of topical medication: (1) prostaglandin analogues only, (2) corticosteroids only, (3) both prostaglandin analogues and corticosteroids, (4) no topical medication. Conjunctival cells were harvested by impression cytology and were examined for inflammatory markers (CD3, CD54, HLA-DR, CCR4, CCR5) by flow cytometry. A tear fluid sample was also examined for inflammatory cytokines (IL-12p70, IL-2, IL-10, IL-8, IL-6, IL-4, IL-5, IFN-gamma, IL-1beta, IFN-alpha, IFN-beta) by multiplex bead arrays.All groups demonstrated increased markers of conjunctival inflammation. There was no significant difference in levels of any inflammatory markers between the four groups, suggesting that the use of topical prostaglandin analogues does not increase conjunctival levels of inflammation beyond those already seen in uveitis.The use of topical prostaglandins does not appear to induce conjunctival inflammation over that which is already present in patients with uveitic glaucoma. This supports the use of topical prostaglandin analogues in patients with uveitic glaucoma, indicating that their use is unlikely to adversely affect subsequent glaucoma filtration surgery through the induction of chronic conjunctival inflammation
Inferring HIV escape rates from multi-locus genotype data
Cytotoxic T-lymphocytes (CTLs) recognize viral protein fragments displayed by
major histocompatibility complex (MHC) molecules on the surface of virally
infected cells and generate an anti-viral response that can kill the infected
cells. Virus variants whose protein fragments are not efficiently presented on
infected cells or whose fragments are presented but not recognized by CTLs
therefore have a competitive advantage and spread rapidly through the
population. We present a method that allows a more robust estimation of these
escape rates from serially sampled sequence data. The proposed method accounts
for competition between multiple escapes by explicitly modeling the
accumulation of escape mutations and the stochastic effects of rare multiple
mutants. Applying our method to serially sampled HIV sequence data, we estimate
rates of HIV escape that are substantially larger than those previously
reported. The method can be extended to complex escapes that require
compensatory mutations. We expect our method to be applicable in other contexts
such as cancer evolution where time series data is also available
Proton beam radiotherapy in the management of uveal melanoma: clinical experience in Scotland
<p>Aim: To evaluate proton-beam radiotherapy (PBRT) in the management of uveal melanoma in Scotland.</p>
<p>Methods: A retrospective review was undertaken on all patients receiving PBRT for uveal melanoma (1994–2005). Data obtained included: gender, past ocular/medical history, age, presenting complaint(s), diagnosis, laterality, tumor location/ultrasound characteristics, visual acuity (VA) and intraocular pressure. At post-treatment reviews (3, 6, 12, and 24 months), the following data was obtained: VA, intraocular pressure, tumor appearance and ultrasound characteristics. Mean follow up was 38.8 months.</p>
<p>Results: Seventy-six patients were included. Mean age was 64 years; male to female ratio was 1.1:1. Ninety-seven percent demonstrated initial treatment response; 87% had successful control of tumor growth. Mean pre-treatment tumor height was 6.2 mm v.s. 4.8 mm post-irradiation (p < 0.001). Pre-irradiation VA was <3/60 in 18.5% compared with 74% post-irradiation (p < 0.0001). There was a statistically significant association between adverse events (enucleation, metastasis) and greater maximal basal tumor diameter. Eighteen eyes were enucleated. The median survival time was estimated to be 54 months.</p>
<p>Conclusion: In our experience, PBRT is a precise, reliable and effective treatment in the management of large, and previously treated uveal melanomas. It prevents enucleation in the majority at short term follow-up.</p>
The diffuse neutrino flux from the inner Galaxy: constraints from very high energy gamma-ray observations
Recently, the MILAGRO collaboration reported on the detection of a diffuse
multi-TeV emission from a region of the Galactic disk close to the inner
Galaxy. The emission is in excess of what is predicted by conventional models
for cosmic ray propagation, which are tuned to reproduce the spectrum of cosmic
rays observed locally. By assuming that the excess detected by MILAGRO is of
hadronic origin and that it is representative for the whole inner Galactic
region, we estimate the expected diffuse flux of neutrinos from a region of the
Galactic disk with coordinates . Our estimate has
to be considered as the maximal expected neutrino flux compatible with all the
available gamma ray data, since any leptonic contribution to the observed
gamma-ray emission would lower the neutrino flux. The diffuse flux of
neutrinos, if close to the maximum allowed level, may be detected by a
km--scale detector located in the northern hemisphere. A detection would
unambiguously reveal the hadronic origin of the diffuse gamma-ray emission.Comment: submitted to Astroparticle Physic
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