1,388 research outputs found
Effects of the tensor force on the ground and first states of the magic Ca nucleus
The magic nature of the Ca nucleus is investigated in the light of the
recent experimental results. We employ both HFB and HF+BCS methods using
Skyrme-type SLy5, SLy5+T and T44 interactions. The evolution of the
single-particle spectra is studied for the N=34 isotones: Fe, Cr,
Ti and Ca. An increase is obtained in the neutron spin-orbit
splittings of and states due to the effect of the tensor force which
also makes Ca a magic nucleus candidate. QRPA calculations on top of
HF+BCS are performed to investigate the first = states of the
calcium isotopic chain. A good agreement for excitation energies is obtained
when we include the tensor force in the mean-field part of the calculations.
The first states indicate a subshell closure for both Ca and
Ca nuclei. We confirm that the tensor part of the interaction is quite
essential in explaining the neutron subshell closure in Ca and Ca
nuclei.Comment: 8 pages, 3 figure
Origin of gamma-ray emission in the shell of Cassiopeia A
Non-thermal X-ray emission from the shell of Cassiopeia A (Cas A) has been an
interesting subject of study, as it provides information about relativistic
electrons and their acceleration mechanisms in the shocks. Chandra X-ray
observatory revealed the detailed spectral and spatial structure of this SNR in
X-rays. The spectral analysis of Chandra X-ray data of Cas A shows unequal flux
levels for different regions of the shell, which can be attributed to different
magnetic fields in those regions. Additionally, the GeV gamma-ray emission
observed by Large Area Telescope on board Fermi Gamma Ray Space Telescope
showed that the hadronic processes are dominating in Cas A, a clear signature
of acceleration of protons. In this paper we aim to explain the GeV-TeV
gamma-ray data in the context of both leptonic and hadronic scenario. We
modeled the multi-wavelength spectrum of Cas A. We use synchrotron emission
process to explain the observed non-thermal X-ray fluxes from different regions
of the shell. These result in estimation of the model parameters, which are
then used to explain TeV gamma-ray emission spectrum. We also use hadronic
scenario to explain both GeV and TeV fluxes simultaneously. We show that a
leptonic model alone cannot explain the GeV-TeV data. Therefore, we need to
invoke a hadronic model to explain the observed GeV-TeV fluxes. We found that
although pure hadronic model is able to explain the GeV-TeV data, a
lepto-hadronic model provides the best fit to the data.Comment: Accepted in A&
Children’s interactions with water in city centres: a case study from Sheffield, UK
Children’s experiences of outdoor environments have been studied now for more than 40 years yet no research has specifically focussed on children’s experiences of water play in constructed spaces of city centres. This article discusses the development of an observational mapping tool, called TOWEC, to record the interaction of children with water. It then reports findings and analysis from observations over a year-long period of 3,399 children interacting with water in the award winning public open space of the Peace Gardens in the centre of the City of Sheffield, UK. The findings reveal that children undertake both active and passive activities associated with the constructed water features and that these activities are influenced by gender, age and temperature, but not ethnicity. The water features were not designed for children to play in but the children realise the potential affordance that the water features provide
Shortcuts through Colocation Facilities
Network overlays, running on top of the existing Internet substrate, are of
perennial value to Internet end-users in the context of, e.g., real-time
applications. Such overlays can employ traffic relays to yield path latencies
lower than the direct paths, a phenomenon known as Triangle Inequality
Violation (TIV). Past studies identify the opportunities of reducing latency
using TIVs. However, they do not investigate the gains of strategically
selecting relays in Colocation Facilities (Colos). In this work, we answer the
following questions: (i) how Colo-hosted relays compare with other relays as
well as with the direct Internet, in terms of latency (RTT) reductions; (ii)
what are the best locations for placing the relays to yield these reductions.
To this end, we conduct a large-scale one-month measurement of inter-domain
paths between RIPE Atlas (RA) nodes as endpoints, located at eyeball networks.
We employ as relays Planetlab nodes, other RA nodes, and machines in Colos. We
examine the RTTs of the overlay paths obtained via the selected relays, as well
as the direct paths. We find that Colo-based relays perform the best and can
achieve latency reductions against direct paths, ranging from a few to 100s of
milliseconds, in 76% of the total cases; 75% (58% of total cases) of these
reductions require only 10 relays in 6 large Colos.Comment: In Proceedings of the ACM Internet Measurement Conference (IMC '17),
London, GB, 201
Lens partition function, pentagon identity and star-triangle relation
We study the three-dimensional lens partition function for
supersymmetric gauge dual theories on by using the gauge/YBE
correspondence. This correspondence relates supersymmetric gauge theories to
exactly solvable models of statistical mechanics. The equality of partition
functions for the three-dimensional supersymmetric dual theories can be written
as an integral identity for hyperbolic hypergeometric functions. We obtain such
an integral identity which can be written as the star-triangle relation for
Ising type integrable models and as the integral pentagon identity. The latter
represents the basic 2-3 Pachner move for triangulated 3-manifolds. A special
case of our integral identity can be used for proving orthogonality and
completeness relation of the Clebsch-Gordan coefficients for the self-dual
continuous series of .Comment: 22 pages, v2: minor corrections and comments, v3: minor correction
The effect of keeping vocabulary notebooks on vocabulary acquisition
Vocabulary notebooks are frequently advocated as a way for students to take control of their vocabulary learning (Fowle, 2002), with the added benefit of improvements in vocabulary learning (Schmitt and Schmitt, 1995; Laufer and Nation, 1999). The study described in this article attempts to lend empirical support to these claims, by investigating the effect of vocabulary notebooks on EFL students' vocabulary acquisition. Students in three lower intermediate EFL classes participated in the study. A vocabulary notebook program was implemented in one class over a 4-week period, with the remaining two classes acting as control groups, following the same curriculum with the same materials but without keeping vocabulary notebooks. Receptive and controlled productive vocabulary tests revealed significantly greater learning of the target words in the treatment group. In addition, students in the treatment group demonstrated a greater tendency to use the target words in free writing compositions. However, a positive impact on learner autonomy - as has been reported in previous studies (McCarthy, 1990) - was not observed. These findings lead the authors to conclude that vocabulary notebooks can be an effective learning tool in EFL classrooms, but positive impacts on learner autonomy may not be seen in the absence of appropriate motivation for language learning. © The Author(s), 2009
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