542 research outputs found
Collaborative Ontology Development — Distributed Architecture and Visualization
In this paper we present the architecture of the browser-based community-driven ontology engineering platform Ontoverse. We will present the architectural needs and designs for an extensible collaborative ontology platform as well as the current implementation based on tuplespaces. In this context we briefly introduce the SQLSpaces and the Semantic Web Application Toolkit (SWAT). To provide interactive collaborative means for editing, merging, and discussing about ontologies adequate visualization techniques are needed to support the ontology designers and ontology users. Therefore we introduce a visualization method called SmartTree that implements focus and context techniques
Modeling the series of (n x 2) Si-rich reconstructions of beta-SiC(001): a prospective atomic wire?
We perform ab initio plane wave supercell density functional calculations on
three candidate models of the (3 x 2) reconstruction of the beta-SiC(001)
surface. We find that the two-adlayer asymmetric-dimer model (TAADM) is
unambiguously favored for all reasonable values of Si chemical potential. We
then use structures derived from the TAADM parent to model the silicon lines
that are observed when the (3 x 2) reconstruction is annealed (the (n x 2)
series of reconstructions), using a tight-binding method. We find that as we
increase n, and so separate the lines, a structural transition occurs in which
the top addimer of the line flattens. We also find that associated with the
separation of the lines is a large decrease in the HOMO-LUMO gap, and that the
HOMO state becomes quasi-one-dimensional. These properties are qualititatively
and quantitatively different from the electronic properties of the original (3
x 2) reconstruction.Comment: 22 pages, including 6 EPS figure
Charge Symmetry Breaking in dd->4He{\pi}0 with WASA-at-COSY
Charge symmetry breaking (CSB) observables are a suitable experimental tool
to examine effects induced by quark masses on the nuclear level. Previous high
precision data from TRIUMF and IUCF are currently used to develop a consistent
description of CSB within the framework of chiral perturbation theory. In this
work the experimental studies on the reaction dd->4He{\pi}0 have been extended
towards higher excess energies in order to provide information on the
contribution of p-waves in the final state. For this, an exclusive measurement
has been carried out at a beam momentum of p=1.2 GeV/c using the WASA-at-COSY
facility. The total cross section amounts to sigma(tot) = (118 +- 18(stat) +-
13(sys) +- 8(ext)) pb and first data on the differential cross section are
consistent with s-wave pion production.Comment: 14 pages, 5 figure
ABC Effect and Resonance Structure in the Double-Pionic Fusion to He
Exclusive and kinematically complete measurements of the double pionic fusion
to He have been performed in the energy region of the so-called ABC effect,
which denotes a pronounced low-mass enhancement in the -invariant mass
spectrum. The experiments were carried out with the WASA detector setup at
COSY. Similar to the observations in the basic reaction
and in the He reaction, the data reveal a correlation
between the ABC effect and a resonance-like energy dependence in the total
cross section. Differential cross sections are well described by the hypothesis
of resonance formation during the reaction process in addition to the
conventional -channel mechanism. The deduced resonance
width can be understood from collision broadening due to Fermi motion of the
nucleons in initial and final nuclei
Cross section ratio and angular distributions of the reaction p + d -> 3He + eta at 48.8 MeV and 59.8 MeV excess energy
We present new data for angular distributions and on the cross section ratio
of the p + d -> 3He + eta reaction at excess energies of Q = 48.8 MeV and Q =
59.8 MeV. The data have been obtained at the WASA-at-COSY experiment
(Forschungszentrum J\"ulich) using a proton beam and a deuterium pellet target.
While the shape of obtained angular distributions show only a slow variation
with the energy, the new results indicate a distinct and unexpected total cross
section fluctuation between Q = 20 MeV and Q = 60 MeV, which might indicate the
variation of the production mechanism within this energy interval.Comment: 9 pages, 9 figure
Neutron-Proton Scattering in the Context of the (2380) Resonance
New data on quasifree polarized neutron-proton scattering, in the region of
the recently observed resonance structure, have been obtained by
exclusive and kinematically complete high-statistics measurements with WASA at
COSY. This paper details the determination of the beam polarization, checks of
the quasifree character of the scattering process, on all obtained
angular distributions and on the new partial-wave analysis, which includes the
new data producing a resonance pole in the - coupled partial
waves at () MeV -- in accordance with the dibaryon
resonance hypothesis. The effect of the new partial-wave solution on the
description of total and differential cross section data as well as specific
combinations of spin-correlation and spin-transfer observables available from
COSY-ANKE measurements at = 2.27 GeV is discussed
Evidence for a New Resonance from Polarized Neutron-Proton Scattering
Exclusive and kinematically complete high-statistics measurements of
quasifree polarized scattering have been performed in the energy
region of the narrow resonance structure with , 2380 MeV/ and 70 MeV observed recently in the
double-pionic fusion channels and .
The experiment was carried out with the WASA detector setup at COSY having a
polarized deuteron beam impinged on the hydrogen pellet target and utilizing
the quasifree process . That way the
analyzing power was measured over a large angular range. The obtained
angular distributions deviate systematically from the current SAID SP07
NN partial-wave solution. Incorporating the new data into the SAID
analysis produces a pole in the waves as expected from the
resonance hypothesis
Observation of in
Using a sample of events recorded with
the BESIII detector at the symmetric electron positron collider BEPCII, we
report the observation of the decay of the charmonium state
into a pair of mesons in the process
. The branching fraction is measured for the first
time to be , where the first uncertainty is
statistical, the second systematic and the third is from the uncertainty of
. The mass and width of the are
determined as MeV/ and
MeV.Comment: 13 pages, 6 figure
Evidence for the decays of and
We study the hadronic decays of to the final states
and , using an annihilation
data sample of 567 pb taken at a center-of-mass energy of 4.6 GeV with
the BESIII detector at the BEPCII collider. We find evidence for the decays
and with
statistical significance of and , respectively.
Normalizing to the reference decays and
, we obtain the ratios of the branching fractions
and to be and , respectively. The upper limits at the 90\% confidence level are
set to be and . Using BESIII measurements of the
branching fractions of the reference decays, we determine
() and
(). Here, the first uncertainties are statistical and the second
systematic. The obtained branching fraction of is
consistent with the previous measurement, and the branching fraction of
is measured for the first
time.Comment: Accepted by Chin. Phys. C : Chin. Phys. C 43, 083002, (2019
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