6,513 research outputs found
An XMM-Newton observation of the globular cluster Omega Centauri
We report on a deep XMM-Newton EPIC observation of the globular cluster Omega
Cen performed on August 13th, 2001. We have detected 11 and 27 faint X-ray
sources in the core and half mass radii, searching down to a luminosity of 1.3
x 10^{31} erg s^{-1} in the 0.5-5 keV range. Most sources have bolometric X-ray
luminosities between ~ 10^{31}-10^{32} erg s^{-1}. We present the color-color
and hardness-intensity diagrams of the source sample, as well as high-quality
EPIC spectra of the brightest objects of the field; including the two candidate
Cataclysmic Variables (CVs) in the core and the quiescent neutron star low-mass
X-ray binary candidate. The spectra of the latter objects fully support their
previous classification. We show that the bulk of sources are hard and
spectrally similar to CVs. The lack of soft faint sources might be related to
the absence of millisecond pulsars in the cluster. The XMM-Newton observations
reveal the presence of an excess of sources well outside the core of the
cluster where several RS CVn binaries have already been found. We have also
analyzed a publicly available Chandra ACIS-I observation performed on January
24-25th, 2000, to improve the XMM-Newton source positions and to search for
source intensity variations between the two data sets. 63 XMM-Newton sources
have a Chandra counterpart, and 15 sources within the half-mass radius have
shown time variability. Overall, the general properties of the faint X-ray
sources in Omega Cen suggest that they are predominantly CVs and active
binaries (RS CVn or BY Dra).Comment: 21 pages, 2 color figures, 8 B&W figures. Accepted for publication in
Astronomy and Astrophysic
Amplification of Isocurvature Perturbations induced by Active-Sterile Neutrino Oscillations
We show how the generation of a lepton number in the Early Universe induced
by active-sterile neutrino oscillations, in presence of small baryon number
inhomogeneities, gives rise to the formation of lepton domains, regions with
different values of active neutrino chemical potential. The structure of these
domains reflects the spectral features of the baryon number inhomogeneities
that generated it. An interesting aspect of the mechanism is that the size of
lepton domains can be super-horizon.Comment: 20 pages + 3 included ps figure
“My journey map”: Developing a qualitative approach to mapping young people’s progress in residential rehabilitation
Young people with substance misuse issues are at risk of harm from significant negative health and life events. Contemporary research notes both a historical failure to recognize the unique needs of adolescents, and the ongoing need for dedicated adolescent treatment programs and outcome measures. It is concerning that there is so little literature assessing the quality, availability, and effectiveness of adolescent-focused treatment programs, and no adolescent-specific measurement tools centered on a young person’s progress in residential treatment. This article reports on the process of developing a qualitative approach to mapping progress in treatment over time. The research seeks to develop an approach that captures, at three points in time and from multiple viewpoints, the progress of young people in four residential rehabilitation services located in New South Wales and Western Australia, across several dimensions of the personal and social aspects of life. Our aim is to develop an approach that is accessible to the alcohol and other drug workforce, and that informs the development of a psychometrically robust quantitative measure of progress that is meaningful and useful both to practitioners and to the young people themselves
First XMM-Newton Observations of the Globular Cluster M22
We have examined preliminary data of the globular cluster, M22, from the EPIC
MOS detectors on board XMM-Newton. We have detected 27 X-ray sources within the
centre of the field of view, 24 of which are new detections. Three sources were
found within the core of the cluster. From spectral analysis of the X-ray
sources, it is possible that the object at the centre of the core is a
quiescent X-ray transient and those lying further out are maybe cataclysmic
variables.Comment: 6 pages, 3 figures, accepted to be published in Astronomy and
Astrophysic
Effect of temperature induced excess porewater pressures on the shaft bearing capacity of geothermal piles
Changes in temperature in clays of low permeability typically induce excess porewater pressures. In the context of geothermal piles this effect has typically been overlooked since most installations have occurred in soils with higher values of permeability. A parametric study is presented that solves the governing differential equations one dimensionally in a pile to study the influence of the various parameters: temperature of the fluid, permeability and soil compressibility. A new shaft resistance reduction ratio has been also defined to illustrate the loss of bearing capacity. The study shows that when the value of permeability is 1E-11 m/s or lower, combined with a soil compressibility in excess of 20,000 MPa, the developed excess porewater pressures can potentially reduce the effective stress locally to very low values. The solution applied to the case of the Lambeth College, London, also provides a plausible explanation to the observed loss of shaft friction of the tested pile
Coupling Of Ribosome And tRNA Dynamics During Translation
Interstellar matter and star formatio
- …