7,233 research outputs found
Study of Radiative Leptonic D Meson Decays
We study the radiative leptonic meson decays of D^+_{(s)}\to
\l^+\nu_{\l}\gamma (\l=e,\mu,\tau), and D^0\to
\l^+\l^-\gamma () within the light front quark model. In the standard
model, we find that the decay branching ratios of , and
are (), (), and
(), and that of D^0\to\l^+\l^-\gamma (\l=e,\mu) and
are and ,
respectively.Comment: 23 pages, 6 Figures, LaTex file, a reference added, to be published
in Mod. Phys. Lett.
The geometric sense of R. Sasaki connection
For the Riemannian manifold two special connections on the sum of the
tangent bundle and the trivial one-dimensional bundle are constructed.
These connections are flat if and only if the space has a constant
sectional curvature . The geometric explanation of this property is
given. This construction gives a coordinate free many-dimensional
generalization of the connection from the paper: R. Sasaki 1979 Soliton
equations and pseudospherical surfaces, Nuclear Phys., {\bf 154 B}, pp.
343-357. It is shown that these connections are in close relation with the
imbedding of into Euclidean or pseudoeuclidean -dimension
spaces.Comment: 7 pages, the key reference to the paper of Min-Oo is included in the
second versio
Ground-State Fidelity and Kosterlitz-Thouless Phase Transition for Spin 1/2 Heisenberg Chain with Next-to-the-Nearest-Neighbor Interaction
The Kosterlitz-Thouless transition for the spin 1/2 Heisenberg chain with the
next-to-the-nearest-neighbor interaction is investigated in the context of an
infinite matrix product state algorithm, which is a generalization of the
infinite time-evolving block decimation algorithm [G. Vidal, Phys. Rev. Lett.
\textbf{98}, 070201 (2007)] to accommodate both the
next-to-the-nearest-neighbor interaction and spontaneous dimerization. It is
found that, in the critical regime, the algorithm automatically leads to
infinite degenerate ground-state wave functions, due to the finiteness of the
truncation dimension. This results in \textit{pseudo} symmetry spontaneous
breakdown, as reflected in a bifurcation in the ground-state fidelity per
lattice site. In addition, this allows to introduce a pseudo-order parameter to
characterize the Kosterlitz-Thouless transition.Comment: 4 pages, 4 figure
A high-resolution oxygen A-band spectrometer (HABS) and its radiation closure
Various studies indicate that high-resolution oxygen A-band spectrum has the
capability to retrieve the vertical profiles of aerosol and cloud properties.
To improve the understanding of oxygen A-band inversions and utility, we
developed a high-resolution oxygen A-band spectrometer (HABS), and deployed
it at Howard University Beltsville site during the NASA Discover Air-Quality
Field Campaign in July, 2011. By using a single telescope, the HABS
instrument measures the direct solar and the zenith diffuse radiation
subsequently. HABS exhibits excellent performance: stable spectral response
ratio, high signal-to-noise ratio (SNR), high-spectrum resolution
(0.016 nm), and high out-of-band rejection (10<sup>−5</sup>). For the spectral
retrievals of HABS measurements, a simulator is developed by combining a
discrete ordinates radiative transfer code (DISORT) with the High Resolution
Transmission (HITRAN) database HITRAN2008. The simulator uses a double-<i>k</i>
approach to reduce the computational cost. The HABS-measured spectra are
consistent with the related simulated spectra. For direct-beam spectra, the
discrepancies between measurements and simulations, indicated by confidence
intervals (95%) of relative difference, are (−0.06, 0.05) and
(−0.08, 0.09) for solar zenith angles of 27 and 72°, respectively.
For zenith diffuse spectra, the related discrepancies between measurements
and simulations are (−0.06, 0.05) and (−0.08, 0.07) for solar zenith
angles of 27 and 72°, respectively. The main discrepancies between
measurements and simulations occur at or near the strong oxygen absorption
line centers. They are mainly due to two kinds of causes: (1) measurement
errors associated with the noise/spikes of HABS-measured spectra, as a result
of combined effects of weak signal, low SNR, and errors in wavelength
registration; (2) modeling errors in the simulation, including the error of
model parameters setting (e.g., oxygen absorption line parameters, vertical
profiles of temperature and pressure) and the lack of treatment of the
rotational Raman scattering. The high-resolution oxygen A-band measurements
from HABS can constrain the active radar retrievals for more accurate cloud
optical properties (e.g., cloud optical depth, effective radius),
particularly for multi-layer clouds and for mixed-phase clouds
Electronic and excitonic properties of two-dimensional and bulk InN crystals
Motivated by potential extensive applications in nanoelectronics devices of III-Vmaterials, we calculate the structural and optoelectronic properties of two-dimensional (2D) InN as well as its three-dimensional (3D) counterparts by using density functional theory (DFT). Compared with the 3D form, the In-N bonding in the 2D InN layer is stronger in terms of the shorter bond length, and the formation of the 2D one is higher in terms of the lower cohesive energy. The bandgap of monolayer InN is 0.31 eV at PBE level and 2.02 eV at GW(0) level. By many-body GW(0) and BSE within RPA calculations, monolayer InN presents an exciton binding energy of 0.12 eV. The fundamental bandgap increases along with layer reduction and is converted from direct (0.7-0.9 eV) in bulk InN to indirect (2.02 eV) in monolayer InN. Under biaxial compressive strain, the bandgap of 2D-InN can be further tuned from indirect to direct
Addressing the unmet need for visualizing Conditional Random Fields in Biological Data
Background: The biological world is replete with phenomena that appear to be
ideally modeled and analyzed by one archetypal statistical framework - the
Graphical Probabilistic Model (GPM). The structure of GPMs is a uniquely good
match for biological problems that range from aligning sequences to modeling
the genome-to-phenome relationship. The fundamental questions that GPMs address
involve making decisions based on a complex web of interacting factors.
Unfortunately, while GPMs ideally fit many questions in biology, they are not
an easy solution to apply. Building a GPM is not a simple task for an end user.
Moreover, applying GPMs is also impeded by the insidious fact that the complex
web of interacting factors inherent to a problem might be easy to define and
also intractable to compute upon. Discussion: We propose that the visualization
sciences can contribute to many domains of the bio-sciences, by developing
tools to address archetypal representation and user interaction issues in GPMs,
and in particular a variety of GPM called a Conditional Random Field(CRF). CRFs
bring additional power, and additional complexity, because the CRF dependency
network can be conditioned on the query data. Conclusions: In this manuscript
we examine the shared features of several biological problems that are amenable
to modeling with CRFs, highlight the challenges that existing visualization and
visual analytics paradigms induce for these data, and document an experimental
solution called StickWRLD which, while leaving room for improvement, has been
successfully applied in several biological research projects.Comment: BioVis 2014 conferenc
Mental Health and Psychosocial Problems of Medical Health Workers during the COVID-19 Epidemic in China
Temperature Dependence of Photoelectrical Properties of Single Selenium Nanowires
Influence of temperature on photoconductivity of single Se nanowires has been studied. Time response of photocurrent at both room temperature and low temperature suggests that the trap states play an important role in the photoelectrical process. Further investigations about light intensity dependence on photocurrent at different temperatures reveal that the trap states significantly affect the carrier generation and recombination. This work may be valuable for improving the device optoelectronic performances by understanding the photoelectrical properties
Dissipative dynamics of vortex lines in superfluid He
We propose a Hamiltonian model that describes the interaction between a
vortex line in superfluid He and the gas of elementary excitations. An
equation of irreversible motion for the density operator of the vortex,
regarded as a macroscopic quantum particle with a finite mass, is derived in
the frame of Generalized Master Equations. This enables us to cast the effect
of the coupling as a drag force with one reactive and one dissipative
component, in agreement with the assumption of the phenomenological theories of
vortex mutual friction in the two fluid model.Comment: 16 pages, no figures, to be published in PR
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