76,337 research outputs found
Three evolutionary paths for magnetar oscillations
Quasi-periodic oscillations have been seen in the light curves following
several magnetar giant flares. These oscillations are of great interest as they
probably provide our first ever view of the normal modes of oscillation of
neutron stars. The state-of-the-art lies in the study of the oscillations of
elastic-magnetic stellar models, mainly with a view to relating the observed
frequencies to the structure and composition of the star itself. We advance
this programme by considering several new physical mechanisms that are likely
to be important for magnetar oscillations. These relate to the
superfluid/superconducting nature of the stellar interior, and the damping of
the modes, both through internal dissipation mechanisms and the launching of
waves into the magnetosphere. We make simple order-of-magnitude estimates to
show that both the frequencies and the damping time of magnetar oscillations
can evolve in time, identifying three distinct `pathways' that can be followed,
depending upon the initial magnitude of the mode excitation. These results are
interesting as they show that the information buried in magnetar QPOs may be
even richer than previously thought, and motivate more careful examination of
magnetar light curves, to search for signatures of the different types of
evolution that we have identified.Comment: To appear in MNRAS. This version reflects changes made in response to
referee's comments, mainly extra discussion in Section 2.
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Supporting reflection and creative thinking by carers of older people with dementia
This vision paper frames requirements engineering as a creative problem solving process. Its purpose is to enable requirements researchers and practitioners to recruit relevant theories, models, techniques and tools from creative problem solving to understand and support requirements processes more effectively. It uses 4 drivers to motivate the case for requirements engineering as a creative problem solving process. It then maps established requirements activities onto one of the longest-established creative problem solving processes, and uses these mappings to locate opportunities for the application of creative problem solving in requirements engineering. The second half of the paper describes selected creativity theories, techniques, software tools and training that can be adopted to improve requirements engineering research and practice. The focus is on support for problem and idea finding - two creative problem solving processes that our investigation revealed are poorly supported in requirements engineering. The paper ends with a research agenda to incorporate creative processes, techniques, training and tools in requirements projects
Cross-correlation of the unresolved X-ray background with faint galaxies
At the faint end of the deepest X-ray surveys, a population of X-ray luminous
galaxies is seen. In this paper, we present the results of a cross-correlation
between the residual, unresolved X-ray photons in a very deep X-ray survey and
the positions of faint galaxies, in order to examine the importance of these
objects at even fainter flux levels. We measure a significant correlation on
all angular scales up to ~1 arcmin. This signal could account for a significant
fraction of the unresolved X-ray background, approximately 35 per cent if the
clustering is similar to optically selected galaxies. However, the angular form
of the correlation is seen to be qualitatively similar to that expected for
clusters of galaxies and the X-ray emission could be associated with hot gas in
clusters or with QSOs within galaxy clusters rather than emission from
individual faint galaxies. The relative contribution from each of these
possibilities cannot be determined with the current data.Comment: 7 pages LaTeX including 9 EPS figures. Uses mn.sty. Accepted for
publication by MNRA
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Requirements Engineering as Creative Problem Solving: A Research Agenda for Idea Finding
This vision paper frames requirements engineering as a creative problem solving process. Its purpose is to enable requirements researchers and practitioners to recruit relevant theories, models, techniques and tools from creative problem solving to understand and support requirements processes more effectively. It uses 4 drivers to motivate the case for requirements engineering as a creative problem solving process. It then maps established requirements activities onto one of the longest-established creative problem solving processes, and uses these mappings to locate opportunities for the application of creative problem solving in requirements engineering. The second half of the paper describes selected creativity theories, techniques, software tools and training that can be adopted to improve requirements engineering research and practice. The focus is on support for problem and idea finding - two creative problem solving processes that our investigation revealed are poorly supported in requirements engineering. The paper ends with a research agenda to incorporate creative processes, techniques, training and tools in requirements projects
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Introducing creativity techniques and software apps to the care of people with dementia
This poster reports research to introduce creative problem solving techniques and software to the care for people with dementia in residential homes
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Facing up to the challenge of behavioural observation in infant hearing assessment
The ability to assess detection and discrimination of speech by infants has proved elusive. Dr Iain Jackson and colleagues discuss how new technologies and fresh approaches might offer valuable insight into young infantsâ behavioural responses to sound
Wheat forecast economics effect study
A model to assess the value of improved information regarding the inventories, productions, exports, and imports of crop on a worldwide basis is discussed. A previously proposed model is interpreted in a stochastic control setting and the underlying assumptions of the model are revealed. In solving the stochastic optimization problem, the Markov programming approach is much more powerful and exact as compared to the dynamic programming-simulation approach of the original model. The convergence of a dual variable Markov programming algorithm is shown to be fast and efficient. A computer program for the general model of multicountry-multiperiod is developed. As an example, the case of one country-two periods is treated and the results are presented in detail. A comparison with the original model results reveals certain interesting aspects of the algorithms and the dependence of the value of information on the incremental cost function
The discovery of very red counterparts to faint X-ray sources
We present deep K-band imaging at the positions of four very faint X-ray
sources found in the UK ROSAT Deep Survey to have no optical counterpart
brighter than R~23. Likely identifications are found within the ROSAT error
circle in all four fields with R-K colours of between 3.2 +/- 0.4 and 6.4 +/-
0.6. From a consideration of the R-K colours and X-ray to optical luminosity
ratios of the candidate identifications, we tentatively classify two of the
X-ray sources as very distant (z ~ 1) clusters of galaxies, one as a narrow
emission line galaxy and one as an obscured QSO.Comment: 7 pages, LaTeX, 7 figures (1 postscript file each). Uses mn.sty and
epsf.sty. Accepted by MNRAS. For more information see
http://www.astro.soton.ac.uk/~amn/UKdee
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