5,525 research outputs found
Structural dynamics in hybrid halide perovskites: Bulk Rashba splitting, spin texture, and carrier localization
The extended carrier lifetime in hybrid halide perovskites was attributed to
a quasi-indirect band gap that arises due to Rashba splitting in both
conduction and valence band edges. In this paper, we present results for an
effective relativistic band structure of (CH3NH3)PbI3 with the focus on the
dispersion of electronic states near the band edges of (CH3NH3)PbI3 affected by
thermal structural fluctuations. We establish a relation between the magnitude
of Rashba splitting and a deviation of Pb-atom from its centrosymmetric site
position in the PbI6 octahedron. For the splitting energy to reach the thermal
energy kT~26 meV (room temperature), the displacement should be of the order
0.3 Ang, which is far above the static displacements of Pb-atoms in the
tetragonal phase of (CH3NH3)PbI3. The significant dynamic enhancement of the
Rashba splitting observed at earlier simulation times (less than 2 ps) later
weakens and becomes less than the thermal energy despite the average
displacement of Pb-atoms remaining large (0.37 Ang). It is randomization of
Pb-displacement vectors and associated cancelation of the net effective
magnetic field acting on electrons at the conduction band edge is responsible
for reduction of the Rashba splitting. The lattice dynamics also leads to
deterioration of Bloch character for states in the valence band leading to
subsequent localization of holes, which affects bipolar mobility of charge
carriers in (CH3NH3)PbI3. These results call into question the quasi-indirect
band gap as a reason for the long carrier lifetime observed in (CH3NH3)PbI3 at
room temperature. An alternative mechanism involves dynamic localization of
holes and their reduced overlap with electrons in reciprocal space.Comment: 12 pages, 11 figures, 1 tabl
Improved Deterministic N-To-One Joint Remote Preparation of an Arbitrary Qubit via EPR Pairs
Recently, Bich et al. (Int. J. Theor. Phys. 51: 2272, 2012) proposed two
deterministic joint remote state preparation (JRSP) protocols of an arbitrary
single-qubit state: one is for two preparers to remotely prepare for a receiver
by using two Einstein-Podolsky-Rosen (ERP) pairs; the other is its generalized
form in the case of arbitrary N>2 preparers via N ERP pairs. In this paper,
Through reviewing and analyzing Bich et al.'s second protocols with N>2
preparers, we find that the success probability P_{suc}=1/4 < 1. In order to
solve the problem, we firstly constructed two sets of projective measurement
bases: the real-coefficient basis and the complex-coefficient one, and further
proposed an improved deterministic N-to-one JRSP protocol for an arbitrary
single-qubit state with unit success probability (i.e, P_{suc}=1). Morever, our
protocol is also flexible and convenient, and it can be used in a practical
network.Comment: 13 pages, 2 figures, two table
Unpaired Photo-to-Caricature Translation on Faces in the Wild
Recently, image-to-image translation has been made much progress owing to the
success of conditional Generative Adversarial Networks (cGANs). And some
unpaired methods based on cycle consistency loss such as DualGAN, CycleGAN and
DiscoGAN are really popular. However, it's still very challenging for
translation tasks with the requirement of high-level visual information
conversion, such as photo-to-caricature translation that requires satire,
exaggeration, lifelikeness and artistry. We present an approach for learning to
translate faces in the wild from the source photo domain to the target
caricature domain with different styles, which can also be used for other
high-level image-to-image translation tasks. In order to capture global
structure with local statistics while translation, we design a dual pathway
model with one coarse discriminator and one fine discriminator. For generator,
we provide one extra perceptual loss in association with adversarial loss and
cycle consistency loss to achieve representation learning for two different
domains. Also the style can be learned by the auxiliary noise input.
Experiments on photo-to-caricature translation of faces in the wild show
considerable performance gain of our proposed method over state-of-the-art
translation methods as well as its potential real applications.Comment: 28 pages, 11 figure
Cryptanalysis and improvement of the quantum private comparison protocol based on Bell entangled states
Recently, Liu et al. [Commun. Theor. Phys. 57, 583, 2012] proposed a quantum
private comparison protocol based on entanglement swapping of Bell states,
which aims to securely compare the equality of two participants' information
with the help of a semi-honest third party (TP). However, this study points out
there is a fatal loophole in this protocol, i.e., TP can obtain all of the two
participants secret inputs without being detected through making a specific
Bell-basis measurement. To fix the problem, a simple solution, which uses
one-time eavesdropper checking with decoy photons instead of twice eavesdropper
checking with Bell states, is demonstrated. Compared with the original
protocol, it also reduces the Bell states consumption and simplifies the steps
in the protocol.Comment: 9 pages, 1 figur
Pipeline Generative Adversarial Networks for Facial Images Generation with Multiple Attributes
Generative Adversarial Networks are proved to be efficient on various kinds
of image generation tasks. However, it is still a challenge if we want to
generate images precisely. Many researchers focus on how to generate images
with one attribute. But image generation under multiple attributes is still a
tough work. In this paper, we try to generate a variety of face images under
multiple constraints using a pipeline process. The Pip-GAN (Pipeline Generative
Adversarial Network) we present employs a pipeline network structure which can
generate a complex facial image step by step using a neutral face image. We
applied our method on two face image databases and demonstrate its ability to
generate convincing novel images of unseen identities under multiple conditions
previously.Comment: 9 pages, 10 figure
Direct Experimental Simulation of the Yang-Baxter Equation
Introduced in the field of many-body statistical mechanics, Yang-Baxter
equation has become an important tool in a variety fields of physics. In this
work, we report the first direct experimental simulation of the Yang-Baxter
equation using linear quantum optics. The equality between the two sides of the
Yang-Baxter equation in two dimension has been demonstrated directly, and the
spectral parameter transformation in the Yang-Baxter equation is explicitly
confirmed.Comment: 7 pages. 6 figure
Instance Map based Image Synthesis with a Denoising Generative Adversarial Network
Semantic layouts based Image synthesizing, which has benefited from the
success of Generative Adversarial Network (GAN), has drawn much attention in
these days. How to enhance the synthesis image equality while keeping the
stochasticity of the GAN is still a challenge. We propose a novel denoising
framework to handle this problem. The overlapped objects generation is another
challenging task when synthesizing images from a semantic layout to a realistic
RGB photo. To overcome this deficiency, we include a one-hot semantic label map
to force the generator paying more attention on the overlapped objects
generation. Furthermore, we improve the loss function of the discriminator by
considering perturb loss and cascade layer loss to guide the generation
process. We applied our methods on the Cityscapes, Facades and NYU datasets and
demonstrate the image generation ability of our model.Comment: 10 pages, 16figure
Productions of and in B decays
We study the productions of p-wave mesons , and
in B decays. By the generalized factorization approach, we find
that the branching ratios of are similar to those of
while the branching ratios of and are and , respectively. In terms of
the observation of by BELLE, we can remove the sign
ambiguity in the mixing angle for physical states and
. In addition, we analyze annihilation contributions in the decays
and we conclude that they could be neglected.Comment: 13 pages, 4 tables, 2 figures, version to appear in Phys. Rev.
Composing Method for the Two-dimensional Scanning Spectra Observed by the New Vacuum Solar Telescope
In this paper we illustrate the technique used by the New Vacuum Solar
Telescope to increase the spatial resolution of two-dimensional (2D) solar
spectroscopy observation involving two dimensions of space and one of
wavelength. Without an image stabilizer at the NVST, a large scale wobble
motion is present during the spatial scanning, whose instantaneous amplitude
could reach up to 1.3" due to the earth's atmosphere and the precision of the
telescope guiding system, and seriously decreases the spatial resolution of 2D
spatial maps composed with the scanning spectra. We make the following effort
to resolve this problem: the imaging system (e.g., the TiO-band) is used to
record and detect the displacement vectors of solar image motion during the
raster scan, in both the slit and scanning directions. The spectral data (e.g.,
the Ha line) which are originally obtained in time sequence are corrected and
re-arranged in space according to those displacement vectors. Raster scans are
carried out in several active regions with different seeing conditions (two
rasters are illustrated in this paper). Given a certain spatial sample and
temporal resolution, the spatial resolution of the composed 2D map could be
close to that of the slit-jaw image. The resulting quality after correction is
quantitatively evaluated with two methods. Two-dimensional physical quantity,
such as the line-of-sight velocities in multi-layer of the solar atmosphere, is
also inferred demonstrating the effect of this technique.Comment: 12 pages, 9 figure
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Impact of low-frequency hotspot mutation R282Q on the structure of p53 DNA-binding domain as revealed by crystallography at 1.54 angstroms resolution.
Tumor suppressor p53 is a sequence-specific DNA-binding protein and its central DNA-binding domain (DBD) harbors six hotspots (Arg175, Gly245, Arg248, Arg249, Arg273 and Arg282) for human cancers. Here, the crystal structure of a low-frequency hotspot mutant, p53DBD(R282Q), is reported at 1.54 angstroms resolution together with the results of molecular-dynamics simulations on the basis of the structure. In addition to eliminating a salt bridge, the R282Q mutation has a significant impact on the properties of two DNA-binding loops (L1 and L3). The L1 loop is flexible in the wild type, but it is not flexible in the mutant. The L3 loop of the wild type is not flexible, whereas it assumes two conformations in the mutant. Molecular-dynamics simulations indicated that both conformations of the L3 loop are accessible under biological conditions. It is predicted that the elimination of the salt bridge and the inversion of the flexibility of L1 and L3 are directly or indirectly responsible for deactivating the tumor suppressor p53
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