23,212 research outputs found
On the Running of the Cosmological Constant in Quantum General Relativity
We present arguments that show what the running of the cosmological constant
means when quantum general relativity is formulated following the prescription
developed by Feynman.Comment: 5 page
ROSAT observations of the dwarf starforming galaxy Holmerg II (UGC 4305)
We present ROSAT PSPC and HRI observations of the dwarf irregular galaxy
Holmberg II (UGC4305). This is one of the most luminous dwarf galaxies (Lx~
10^{40} erg s^{-1} cm^{-2}) detected in the ROSAT All-Sky Survey. The X-ray
emission comes from a single unresolved point source, coincident with a large
HII region which emits intense radio emission. The source is variable on both
year and day timescales, clearly favouring accretion into a compact object
rather than a supernova remnant or a superbubble interpretation for the origin
of the X-ray emission. However, its X-ray spectrum is well-fit by a a
Raymond-Smith spectrum with kT~0.8 keV, lower than the temperature of X-ray
binaries in nearby spiral galaxies.Comment: Accepted for publication in MNRA
Resummed Quantum Gravity
We present the current status of the a new approach to quantum general
relativity based on the exact resummation of its perturbative series as that
series was formulated by Feynman. We show that the resummed theory is UV finite
and we present some phenomenological applications as well.Comment: 4 pages, 1 figure; presented at ICHEP0
ROSAT and ASCA Observations of X-ray Luminous starburst Galaxies : NGC3310 and NGC3690
We present ROSAT (HRI and PSPC) and ASCA observations of the two luminous
(L_x ~10^{41-42} erg s^{-1}) star-forming galaxies NGC3310 and NGC3690.
The HRI shows clearly that the sources are extended with the X-ray emission
in NGC3690 coming from at least three regions. The combined 0.1-10 keV spectrum
of NGC3310 can be described by two components, a Raymond-Smith plasma with
temperature kT=0.81^{+0.09}_{-0.12} keV and a hard power-law,
Gamma=1.44^{+0.20}_{-0.11}, (or alternatively a harder Raymond-Smith plasma
with kT ~15 keV), while there is no substantial excess absorption above the
Galactic. The soft component emission is probably due to a super-wind while the
nature of the hard emission is more uncertain with likely origins, X-ray
binaries, inverse Compton scattering of IR photons, an AGN or a very hot gas
component (~10^8 K). The spectrum of NGC3690 is similar, with
kT=0.83^{+0.02}_{-0.04} keV and Gamma=1.56^{+0.11}_{-0.11}. We also employ more
complicated models such as a multi-temperature thermal plasma, a
non-equilibrium ionization code or the addition of a third softer component
which improve the fit but not at a statistically significant level (<2sigma).
These results are similar to recent results on the archetypal star-forming
galaxies M82 and NGC253.Comment: Latex, 11 pages, 1 landascape table, Accepted for publication in
MNRA
A note on the appearance of self-dual Yang-Mills fields in integrable hierarchies
A family of mappings from the solution spaces of certain generalized
Drinfeld-Sokolov hierarchies to the self-dual Yang-Mills system on R^{2,2} is
described. This provides an extension of the well-known relationship between
self-dual connections and integrable hierarchies of AKNS and Drinfeld-Sokolov
type
Microsatellite-stable diploid carcinoma: a biologically distinct and aggressive subset of sporadic colorectal cancer
Chromosomal instability and microsatellite instability represent the major pathways for colorectal cancer (CRC) progression. However, a significant percentage of CRC shows neither pattern of instability, and thus represents a potentially distinctive form of the disease. Flow cytometry was used to determine the degree of DNA aneuploidy in 46 consecutive sporadic colorectal cancers. Microsatellite status was determined by PCR amplification using standard markers, while immunostaining was used to examine the expression of p53. K- ras status was determined by restriction-mediated PCR assay. Twenty-five (54%) tumours were aneuploid, 14 (30%) were diploid and microsatellite-stable and seven (15%) were diploid and microsatellite-unstable. Tumours with microsatellite instability were more likely to be right sided, to occur in women and to be associated with an improved survival. Aneuploid tumours were significantly more common in men and were likely to be left sided. The diploid microsatellite-stable (MSS) tumours did not show a sex or site predilection, but were strongly associated with the presence of metastatic disease at the time of diagnosis. Our data suggests that diploid, MSS tumours represent a biologically and phenotypically distinct subset of colorectal carcinoma, and one that is associated with the early development of metastases. We suggest that the genetic stability that characterizes these tumours may favour the maintenance of an invasive phenotype, and thus facilitate disease progression. These findings may have important implications for treatment options in this disease subset. © 2001 Cancer Research Campaign http://www.bjcancer.co
Use of tri-axial accelerometers to assess terrestrial mammal behaviour in the wild
Tri-axial accelerometer tags provide quantitative data on body movement that can be used to characterize behaviour and understand species ecology in ways that would otherwise be impossible. Using tags on wild terrestrial mammals, especially smaller species, in natural settings has been limited. Poor battery power also reduced the amount of data collected, which limits what can be derived about animal behaviour. Another challenge using wild animals, is acquiring observations of actual behaviours with which to compare tag data and create an adequate training set to reliably identify behavioural states. Brown hares were fitted with accelerometers for 5 weeks to evaluate their use in collecting detailed behaviour data and activity levels. Collared hares were filmed to associate actual behaviours with tag data. Observed behaviours were classified using Random Forests (ensemble learning method) to create a supervised model and then used to classify hare behaviour from the tags. Increased tag longevity allowed acquisition of large quantities of data from each individual and direct observation of tagged hare's behaviour. Random Forests accurately classified observed behaviours from tag data with an 11% error rate. Individual accuracy of behaviours varied with running (100% accuracy), feeding (94.7%) and vigilance (98.3%) having the highest classification accuracy. Hares spent 46% of their time being vigilant and 25% feeding when active. The combination of our tags and Random Forests facilitated large amounts of behavioural data to be collected on animals where observational studies could be limited, or impossible. The same method could be used on a range of terrestrial mammals to create models to investigate behaviour from tag data, to learn more about their behaviour and be used to answer many ecological questions. However, further development of methods for analysing tag data is needed to make the process quicker, simpler and more accurate
The dispersive self-dual Einstein equations and the Toda lattice
The Boyer-Finley equation, or -Toda equation is both a reduction
of the self-dual Einstein equations and the dispersionlesslimit of the
-Toda lattice equation. This suggests that there should be a dispersive
version of the self-dual Einstein equation which both contains the Toda lattice
equation and whose dispersionless limit is the familiar self-dual Einstein
equation. Such a system is studied in this paper. The results are achieved by
using a deformation, based on an associative -product, of the algebra
used in the study of the undeformed, or dispersionless,
equations.Comment: 11 pages, LaTeX. To appear: J. Phys.
Structural basis of the effect of activating mutations on the EGF receptor
Mutations within the kinase domain of the epidermal growth factor receptor (EGFR) are common oncogenic driver events in non-small cell lung cancer. Although the activation of EGFR in normal cells is primarily driven by growth-factor-binding-induced dimerization, mutations on different exons of the kinase domain of the receptor have been found to affect the equilibrium between its active and inactive conformations giving rise to growth-factor-independent kinase activation. Using molecular dynamics simulations combined with enhanced sampling techniques, we compare here the conformational landscape of the monomers and homodimers of the wild-type and mutated forms of EGFR ΔELREA and L858R, as well as of two exon 20 insertions, D770-N771insNPG, and A763-Y764insFQEA. The differences in the conformational energy landscapes are consistent with multiple mechanisms of action including the regulation of the hinge motion, the stabilization of the dimeric interface, and local unfolding transitions. Overall, a combination of different effects is caused by the mutations and leads to the observed aberrant signaling
The development and application of audit criteria for assessing knowledge exchange plans in health research grant applications.
Background: Research funders expect evidence of end user engagement and impact plans in research proposals. Drawing upon existing frameworks, we developed audit criteria to help researchers and their institutions assess the knowledge exchange plans of health research proposals. Findings: Criteria clustered around five themes: problem definition; involvement of research users; public and patient engagement; dissemination and implementation; and planning, management and evaluation of knowledge exchange. We applied these to a sample of grant applications from one research institution in the United Kingdom to demonstrate feasibility. Conclusion: Our criteria may be useful as a tool for researcher self-assessment and for research institutions to assess the quality of knowledge exchange plans and identify areas for systematic improvement
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