798 research outputs found
The hot gas content of fossil galaxy clusters
We investigate the properties of the hot gas in four fossil galaxy systems
detected at high significance in the Planck Sunyaev-Zeldovich (SZ) survey.
XMM-Newton observations reveal overall temperatures of kT ~ 5-6 keV and yield
hydrostatic masses M500,HE > 3.5 x 10e14 Msun, confirming their nature as bona
fide massive clusters. We measure the thermodynamic properties of the hot gas
in X-rays (out to beyond R500 in three cases) and derive their individual
pressure profiles out to R ~ 2.5 R500 with the SZ data. We combine the X-ray
and SZ data to measure hydrostatic mass profiles and to examine the hot gas
content and its radial distribution. The average Navarro-Frenk-White (NFW)
concentration parameter, c500 = 3.2 +/- 0.4, is the same as that of relaxed
`normal' clusters. The gas mass fraction profiles exhibit striking variation in
the inner regions, but converge to approximately the cosmic baryon fraction
(corrected for depletion) at R500. Beyond R500 the gas mass fraction profiles
again diverge, which we interpret as being due to a difference in gas clumping
and/or a breakdown of hydrostatic equilibrium in the external regions. Overall
our observations point to considerable radial variation in the hot gas content
and in the gas clumping and/or hydrostatic equilibrium properties in these
fossil clusters, at odds with the interpretation of their being old, evolved
and undisturbed. At least some fossil objects appear to be dynamically young.Comment: 4 pages, 2 figures. Accepted for publication in A&
Asymptotic Conformal Yano--Killing Tensors for Schwarzschild Metric
The asymptotic conformal Yano--Killing tensor proposed in J. Jezierski, On
the relation between metric and spin-2 formulation of linearized Einstein
theory [GRG, in print (1994)] is analyzed for Schwarzschild metric and tensor
equations defining this object are given. The result shows that the
Schwarzschild metric (and other metrics which are asymptotically
``Schwarzschildean'' up to O(1/r^2) at spatial infinity) is among the metrics
fullfilling stronger asymptotic conditions and supertranslations ambiguities
disappear. It is also clear from the result that 14 asymptotic gravitational
charges are well defined on the ``Schwarzschildean'' background.Comment: 8 pages, latex, no figure
Phase II study of a short course of weekly high-dose cisplatin combined with long-term oral etoposide in metastatic colorectal cancer.
In a phase I study of weekly administered cisplatin combined with oral etoposide, we observed a partial response in 4 out of 11 patients with metastatic colorectal cancer. Subsequently, we performed a phase II study to investigate the activity of this combination as first-line treatment in this disease. Fourteen patients with metastatic colorectal cancer were enrolled in this study. Treatment consisted of cisplatin, administered in 3% sodium chloride, at a dose of 70 mg m-2 on days 1, 8 and 15 and days 29, 36 and 43 combined with oral etoposide 50 mg absolute dose daily on days 1-15 of both courses. Patients with stable disease or better continued treatment with etoposide 50 mg m-2 orally on days 1-21 every 28 days. A partial response was observed in two patients with liver metastases (14%; 95% confidence limits 2-42%) for 30 and 32 weeks. Five patients had stable disease. Toxicity consisted mainly of anaemia, leucocytopenia, nausea and vomiting. Tinnitus was reported by six patients. The activity of the combination cisplatin-oral etoposide in the schedule is only minimal in metastatic colorectal cancer
Antibodies against p53 are associated with poor prognosis of colorectal cancer.
Mutation of the p53 gene is a common event in colorectal cancer. This alteration can result in cellular accumulation of p53 and may also induce p53 antibodies. Accumulation of p53 in tumour cells has been associated with poor prognosis of colorectal cancer. We tested preoperative sera from 255 patients with colorectal cancer by enzyme-linked immunosorbent assay (ELISA). A total of 70.2% had reactivity that was higher than the 'low' control serum. Employing a cut-off level of 10% of the 'high' control sample, 25.5% of the patients were positive for p53 antibodies. The presence of p53 antibodies correlated with the following prognostic factors: histological differentiation grade, shape of the tumour, and tumour invasion into blood vessels. Patients with p53 antibodies were shown to have decreased survival and decreased disease-free survival. Specifically for patients with cancer stage A and B1 the presence of p53 antibodies selected a subgroup with poor prognosis
A Kinematic Approach To Assessing Environmental Effects: Star-Forming Galaxies in a z~0.9 SpARCS cluster using Spitzer 24um Observations
We present an infrared study of a z=0.872 cluster, SpARCS J161314+564930,
with the primary aim of distinguishing the dynamical histories of
spectroscopically confirmed star-forming members to assess the role of cluster
environment. We utilize deep MIPS imaging and a mass-limited sample of 85
spectroscopic members to identify 16 24um-bright sources within the cluster,
and measure their 24um star formation rates (SFRs) down to ~6 Msolar/year.
Based on their line-of-sight velocities and stellar ages, MIPS cluster members
appear to be an infalling population that was recently accreted from the field
with minimal environmental dependency on their star formation. However, we
identify a double-sequenced distribution of star-forming galaxies amongst the
members, with one branch exhibiting declining specific SFRs with mass. The
members along this sub-main sequence contain spectral features suggestive of
passive galaxies. Using caustic diagrams, we kinematically identify these
galaxies as a virialized and/or backsplash population. Moreover, we find a mix
of dynamical histories at all projected radii, indicating that standard
definitions of environment (i.e., radius and density) are contaminated with
recently accreted interlopers, which could contribute to a lack of
environmental trends for star-forming galaxies. A cleaner narrative of their
dynamical past begins to unfold when using a proxy for accretion histories
through profiles of constant (r/r_200)x(Delta v/sigma_v); galaxies accreted at
earlier times possess lower values of (r/r_200)x(Delta v/sigma_v) with minimal
contamination from the distinct infalling population. Therefore, adopting a
time-averaged definition for density (as traced by accretion histories) rather
than an instantaneous density yields a depressed specific SFR within the
dynamical cluster core.Comment: 14 pages, 10 figures, 1 table; accepted for publication in Ap
"Peeling property" for linearized gravity in null coordinates
A complete description of the linearized gravitational field on a flat
background is given in terms of gauge-independent quasilocal quantities. This
is an extension of the results from gr-qc/9801068. Asymptotic spherical
quasilocal parameterization of the Weyl field and its relation with Einstein
equations is presented. The field equations are equivalent to the wave
equation. A generalization for Schwarzschild background is developed and the
axial part of gravitational field is fully analyzed. In the case of axial
degree of freedom for linearized gravitational field the corresponding
generalization of the d'Alembert operator is a Regge-Wheeler equation. Finally,
the asymptotics at null infinity is investigated and strong peeling property
for axial waves is proved.Comment: 27 page
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