18,333 research outputs found
Charge centers in CaF: Ab initio calculation of elementary physical properties
Charge centers in ionic crystals provide a channel for elementary interaction
between electromagnetic radiation and the lattice. We calculate the electronic
ground state energies which are needed to create a charge center -- namely a
- and a -center. In well agreement with common understanding the
-center results in being accompanied by a small lattice distortion whereas
the -center is accompanied by a very large lattice deformation. Opposite to
the common understanding the additional positive charge in the charge center
results rather to be localized on a F complex than on a
F-complex. From the ground states of the charge centers we derive binding
energies, diffusion barriers and agglomeration energies for -center
formation. These microscopic quantities are of fundamental interest to
understand the dynamic processes which are initiated if the crystals interact
with extreme intense deep ultra violet radiation. We further derive the
equilibrium concentrations of charge centers in grown crystals.Comment: to appear in Phys. Rev. B in Aug. 2006, 11 Fig
Ward Round in Moyo House: Management issues in malnourished children with HIV and Tuberculosis (TB)
No Abstrac
Fully three dimensional breather solitons can be created using Feshbach resonance
We investigate the stability properties of breather solitons in a
three-dimensional Bose-Einstein Condensate with Feshbach Resonance Management
of the scattering length and con ned only by a one dimensional optical lattice.
We compare regions of stability in parameter space obtained from a fully 3D
analysis with those from a quasi two-dimensional treatment. For moderate con
nement we discover a new island of stability in the 3D case, not present in the
quasi 2D treatment. Stable solutions from this region have nontrivial dynamics
in the lattice direction, hence they describe fully 3D breather solitons. We
demonstrate these solutions in direct numerical simulations and outline a
possible way of creating robust 3D solitons in experiments in a Bose Einstein
Condensate in a one-dimensional lattice. We point other possible applications.Comment: 4 pages, 4 figures; accepted to Physical Review Letter
The role of the individual in the coming era of process-based therapy
For decades the development of evidence-based therapy has been based on experimental tests of protocols designed to impact psychiatric syndromes. As this paradigm weakens, a more process-based therapy approach is rising in its place, focused on how to best target and change core biopsychosocial processes in specific situations for given goals with given clients. This is an inherently more idiographic question than has normally been at issue in evidence-based therapy over the last few decades. In this article we explore methods of assessment and analysis that can integrate idiographic and nomothetic approaches in a process-based era.Accepted manuscrip
SCOOTER: A compact and scalable dynamic labeling scheme for XML updates
Although dynamic labeling schemes for XML have been the
focus of recent research activity, there are significant challenges still to be overcome. In particular, though there are labeling schemes that ensure a compact label representation when creating an XML document, when the document is subject to repeated and arbitrary deletions and insertions, the labels grow rapidly and consequently have a significant impact on query and update performance. We review the outstanding issues todate and in this paper we propose SCOOTER - a new dynamic labeling scheme for XML. The new labeling scheme can completely avoid relabeling
existing labels. In particular, SCOOTER can handle frequently skewed insertions gracefully. Theoretical analysis and experimental results confirm the scalability, compact representation, efficient growth rate and performance of SCOOTER in comparison to existing dynamic labeling schemes
Probing gas and dust in the tidal tail of NGC 5221 with the type Ia supernova iPTF16abc
Context. Type Ia supernovae (SNe Ia) can be used to address numerous
questions in astrophysics and cosmology. Due to their well known spectral and
photometric properties, SNe Ia are well suited to study gas and dust along the
lines-of-sight to the explosions. For example, narrow Na I D and Ca II H&K
absorption lines can be studied easily, because of the well-defined spectral
continuum of SNe Ia around these features. Aims. We study the gas and dust
along the line-of-sight to iPTF16abc, which occurred in an unusual location, in
a tidal arm, 80 kpc from centre of the galaxy NGC 5221. Methods. Using a
time-series of high-resolution spectra, we examine narrow Na I D and Ca II H&K
absorption features for variations in time, which would be indicative for
circumstellar (CS) matter. Furthermore, we take advantage of the well known
photometric properties of SNe Ia to determine reddening due to dust along the
line-of-sight. Results. From the lack of variations in Na I D and Ca II H&K, we
determine that none of the detected absorption features originate from the CS
medium of iPTF16abc. While the Na I D and Ca II H&K absorption is found to be
optically thick, a negligible amount of reddening points to a small column of
interstellar dust. Conclusions. We find that the gas along the line-of-sight to
iPTF16abc is typical of what might be found in the interstellar medium (ISM)
within a galaxy. It suggests that we are observing gas that has been tidally
stripped during an interaction of NGC 5221 with one of its neighbouring
galaxies in the past years. In the future, the gas clouds could
become the locations of star formation. On a longer time scale, the clouds
might diffuse, enriching the circum-galactic medium (CGM) with metals. The gas
profile along the line-of-sight should be useful for future studies of the
dynamics of the galaxy group containing NGC 5221.Comment: 8 pages, 6 figure
Mobile Access in the Library: Some New Developments in Ireland
New insights provided by a range of specialists in the areas of social science, cognitive research and computer science research have led to increased developments and advances in the architectures for interactive and mobile learning environments. The most exciting results indicate that mobile technologies can be used to revolutionize learning and provided discontinuous rather than incremental learning opportunities in libraries and campuses worldwide. Mobile learning corroborates the view of educational philosophers such as Dewey and McLuhan that there is an intrinsic connection between communication, information provision and the learner community. Nevertheless, despite the rapid and continuing adoption of mobile devices, there has, to date, been little activity in integrating these technologies into the realm of mobile learning and the learning and library/information environments. A paradigm shift is occurring in the access people have to educational materials due to the ubiquitous availability of these materials brought about by the mobility and pervasiveness factors, which are inherent to mobile technologies. The potential for mobile technologies in education is enormous and the challenge for the e-learning community is to harness these devices for the benefit of education. One such benefit is the ever-increasing availability of educational content such as e-books on mobile devices. The availability of e-books will greatly support mobile access in the library
Progress with air quality management in the 60 years since the UK clean air act, 1956. Lessons, failures, challenges and opportunities
© 2016 WIT Press, www.witpress.com. This paper explores the challenges, opportunities and progress made with managing air quality since the United Kingdom parliament passed the Clean Air Act, 1956. It seeks to identify the factors contributing to successful management of air quality and the factors that have acted, or continue to do so, as barriers to progress. The public health catastrophe of the 1952 London Smog created the political momentum for the 1956 Act to be passed. The nature of the contemporary air pollution challenge is reviewed in terms of the public health burden, the economic cost and the governmental response. The contemporary response is considered inadequate for the scale and intensity of the problem
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