12,333 research outputs found
Role of Li_2B_(12)H_(12) for the Formation and Decomposition of LiBH_4
By in situ X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) spectroscopy, the role
of Li_2B_(12)H_(12) for the sorption of LiBH_4 is analyzed. We demonstrate that Li_2B_(12)H_(12) and an
amorphous Li_2B_(10)H_(10) phase are formed by the reaction of LiBH_4 with diborane (B_2H_6) at 200 °C.
Based on our present results, we propose that the Li -2B - (12)H_(12) formation in the desorption of LiBH_4 can
be explained as a result of reaction of diborane and LiBH_4. This reaction of the borohydride with
diborane may also be observed for other borohydrides, where B_(12)H_(12) phases are found during
decomposition
Variational study of a two-level system coupled to a harmonic oscillator in a ultrastrong coupling regime
The nonclassical behaviors of a two-level system coupled to a harmonic
oscillator is investigated in the ultrastrong coupling regime. We revisit the
variational solution of the ground state and find that the existing solution do
not account accurately for nonclassical effects such squeezing. We suggest a
new trial wave function and demonstrate that it has an excellent accuracy on
the quantum correlation effects as well as on energy.Comment: 4 pages; 3 figures; to appear in Phys. Rev.
Observational constraints on a unified dark matter and dark energy model based on generalized Chaplygin gas
We study a generalized version of Chaplygin gas as unified model of dark
matter and dark energy. Using realistic theoretical models and the currently
available observational data from the age of the universe, the expansion
history based on the type Ia supernovae, the matter power spectrum, the cosmic
microwave background radiation anisotropy power spectra, and the perturbation
growth factor we put the unified model under observational test. As the model
has only two free parameters in the flat Friedmann background [CDM
(cold dark matter) model has only one free parameter] we show that the model is
already tightly constrained by currently available observations. The only
parameter space extremely close to the CDM model is allowed in this
unified model.Comment: 7 pages, 9 figure
Duality between N=5 and N=6 Chern-Simons matter theory
We provide evidences for the duality between Chern-Simons matter theory and theory for a suitable by working out the
superconformal index, which shows perfect matching. For theories,
we show that supersymmetry is enhanced to by explicitly
constructing monopole operators filling in -currents. Finally we
work out the large index of and show that
it exactly matches with the gravity index on , which
further provides additional evidence for the duality between the
and theory for Comment: 15 pages; references adde
Improving the Segmentation of Anatomical Structures in Chest Radiographs using U-Net with an ImageNet Pre-trained Encoder
Accurate segmentation of anatomical structures in chest radiographs is
essential for many computer-aided diagnosis tasks. In this paper we investigate
the latest fully-convolutional architectures for the task of multi-class
segmentation of the lungs field, heart and clavicles in a chest radiograph. In
addition, we explore the influence of using different loss functions in the
training process of a neural network for semantic segmentation. We evaluate all
models on a common benchmark of 247 X-ray images from the JSRT database and
ground-truth segmentation masks from the SCR dataset. Our best performing
architecture, is a modified U-Net that benefits from pre-trained encoder
weights. This model outperformed the current state-of-the-art methods tested on
the same benchmark, with Jaccard overlap scores of 96.1% for lung fields, 90.6%
for heart and 85.5% for clavicles.Comment: Presented at the First International Workshop on Thoracic Image
Analysis (TIA), MICCAI 201
Lines on projective varieties and applications
The first part of this note contains a review of basic properties of the
variety of lines contained in an embedded projective variety and passing
through a general point. In particular we provide a detailed proof that for
varieties defined by quadratic equations the base locus of the projective
second fundamental form at a general point coincides, as a scheme, with the
variety of lines. The second part concerns the problem of extending embedded
projective manifolds, using the geometry of the variety of lines. Some
applications to the case of homogeneous manifolds are included.Comment: 15 pages. One example removed; one remark and some references added;
typos correcte
Index for Three Dimensional Superconformal Field Theories and Its Applications
We review aspects of superconformal indices in three dimension. Three
dimensional superconformal indices can be exactly computed by using
localization method including monopole contribution, and can be applied to
provide evidences for mirror duality, AdS_4/CFT_3 correspondence and global
symmetry enhancement of strongly coupled gauge theories. After reviewing, we
discuss the possibility of global symmetry enhancement in a finite rank of
gauge group.Comment: 14 pages, Proceedings of the Seventh International Conference Quantum
Theory and Symmetries (QTS-7) in Prague, Czech Republic, August, 2011; v2:
minor modifications, discussion of supersymmetry enhancement of abelian ABJM
theory by using an index were adde
Cohomological characterizations of projective spaces and hyperquadrics
We confirm Beauville's conjecture that claims that if the p-th exterior power
of the tangent bundle of a smooth projective variety contains the p-th power of
an ample line bundle, then the variety is either the projective space or the
p-dimensional quadric hypersurface.Comment: Added Lemma 2.8 and slightly changed proof of Lemma 6.2 to make them
apply for torsion-free sheaves and not only to vector bundle
Possible evidence of non-Fermi liquid behavior from quasi-one-dimensional indium nanowires
We report possible evidence of non-Fermi liquid (NFL) observed at room
temperature from the quasi one-dimensional (1D) indium (In) nanowires
self-assembled on Si(111)-77 surface. Using high-resolution
electron-energy-loss spectroscopy, we have measured energy and width
dispersions of a low energy intrasubband plasmon excitation in the In
nanowires. We observe the energy-momentum dispersion (q) in the low q
limit exactly as predicted by both NFL theory and the
random-phase-approximation. The unusual non-analytic width dispersion measured with an exponent =1.400.24, however,
is understood only by the NFL theory. Such an abnormal width dispersion of low
energy excitations may probe the NFL feature of a non-ideal 1D interacting
electron system despite the significantly suppressed spin-charge separation
(40 meV).Comment: 11 pages and 4 figure
A Quantum Rosetta Stone for Interferometry
Heisenberg-limited measurement protocols can be used to gain an increase in
measurement precision over classical protocols. Such measurements can be
implemented using, e.g., optical Mach-Zehnder interferometers and Ramsey
spectroscopes. We address the formal equivalence between the Mach-Zehnder
interferometer, the Ramsey spectroscope, and the discrete Fourier transform.
Based on this equivalence we introduce the ``quantum Rosetta stone'', and we
describe a projective-measurement scheme for generating the desired
correlations between the interferometric input states in order to achieve
Heisenberg-limited sensitivity. The Rosetta stone then tells us the same method
should work in atom spectroscopy.Comment: 8 pages, 4 figure
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