893 research outputs found
Orbital density wave induced by electron-lattice coupling in orthorhombic iron pnictides
In this paper we explore the magnetic and orbital properties closely related
to a tetragonal-orthorhombic structural phase transition in iron pnictides
based on both two- and five-orbital Hubbard models. The electron-lattice
coupling, which interplays with electronic interaction, is self-consistently
treated. Our results reveal that the orbital polarization stabilizes the spin
density wave (SDW) order in both tetragonal and orthorhombic phases. However,
the ferro-orbital density wave (F-ODW) only occurs in the orthorhombic phase
rather than in the tetragonal one. Magnetic moments of Fe are small in the
intermediate Coulomb interaction region for the striped antiferromangnetic
phase in the realistic five orbital model. The anisotropic Fermi surface in the
SDW/ODW orthorhombic phase is well in agreement with the recent angle-resolved
photoemission spectroscopy experiments. These results suggest a scenario that
the magnetic phase transition is driven by the ODW order mainly arising from
the electron-lattice coupling.Comment: 21 pages, 10 figure
Relightable and Animatable Neural Avatars from Videos
Lightweight creation of 3D digital avatars is a highly desirable but
challenging task. With only sparse videos of a person under unknown
illumination, we propose a method to create relightable and animatable neural
avatars, which can be used to synthesize photorealistic images of humans under
novel viewpoints, body poses, and lighting. The key challenge here is to
disentangle the geometry, material of the clothed body, and lighting, which
becomes more difficult due to the complex geometry and shadow changes caused by
body motions. To solve this ill-posed problem, we propose novel techniques to
better model the geometry and shadow changes. For geometry change modeling, we
propose an invertible deformation field, which helps to solve the inverse
skinning problem and leads to better geometry quality. To model the spatial and
temporal varying shading cues, we propose a pose-aware part-wise light
visibility network to estimate light occlusion. Extensive experiments on
synthetic and real datasets show that our approach reconstructs high-quality
geometry and generates realistic shadows under different body poses. Code and
data are available at
\url{https://wenbin-lin.github.io/RelightableAvatar-page/}.Comment: Accepted by AAAI 202
Determination of the superconducting gap in near optimally doped Bi_2Sr_{2-x}La_xCuO_{6+\delta} (x ~ 0.4) from low-temperature specific heat
Low-temperature specific heat of the monolayer high-Tc superconductor
Bi_2Sr_{2-x}La_xCuO_{6+\delta} has been measured close to the optimal doping
point (x ~ 0.4) in different magnetic fields. The identification of both a T^2
term in zero field and a \sqrt{H} dependence of the specific heat in fields is
shown to follow the theoretical prediction for d-wave pairing, which enables us
to extract the slope of the superconducting gap in the vicinity of the nodes
(v_{\Delta}, which is proportional to the superconducting gap \Delta_0 at the
antinodes according to the standard d_{x^2-y^2} gap function). The v_{\Delta}
or \Delta_0 (~ 12 meV) determined from this bulk measurement shows close
agreement with that obtained from spectroscopy or tunneling measurements, which
confirms the simple d-wave form of the superconducting gap.Comment: 5 pages, 4 figures, 1 tabl
Dissecting horizontal and vertical gene transfer of antibiotic resistance plasmid in bacterial community using microfluidics
The spread of antibiotic resistance genes (ARGs) has become an emerging threat to the global health. Although horizontal gene transfer (HGT) is regarded as one of the major pathways, more evidence has shown the significant involvement of vertical gene transfer (VGT). However, traditional cultivation-based methods cannot distinguish HGT and VGT, resulting in often contradictory conclusions. Here, single-cell microfluidics with time-lapse imaging has been successfully employed to dissect the contribution of plasmid-mediated HGT and VGT to ARG transmission in an environmental community. Using Escherichia coli with an ARG-coded plasmid pKJK5 with trimethoprim resistance as the donor, we quantified the effects of three representative antibiotics (trimethoprim, tetracycline and amoxicillin) on the ARG transfer process in an activated sludge bacterial community. It was found that HGT was influenced by the inhibitory mechanism of an antibiotic and its targets (donor, recipient alone or together), whereas VGT contributes significantly to the formation of transconjugants and consequently ARG spreading. Trimethoprim is highly resisted by the donor and transconjugants, and its presence significantly increased both the HGT and VGT rates. Although tetracycline and amoxicillin both inhibit the donor, they showed different effects on HGT rate as a result of different inhibitory mechanisms. Furthermore, we show the kinetics of HGT in a community can be described using an epidemic infection model, which in combination with quantitative measure of HGT and VGT on chip provides a promising tool to study and predict the dynamics of ARG spread in real-world communities
Source attack of decoy-state quantum key distribution using phase information
Quantum key distribution (QKD) utilizes the laws of quantum mechanics to
achieve information-theoretically secure key generation. This field is now
approaching the stage of commercialization, but many practical QKD systems
still suffer from security loopholes due to imperfect devices. In fact,
practical attacks have successfully been demonstrated. Fortunately, most of
them only exploit detection-side loopholes which are now closed by the recent
idea of measurement-device-independent QKD. On the other hand, little attention
is paid to the source which may still leave QKD systems insecure. In this work,
we propose and demonstrate an attack that exploits a source-side loophole
existing in qubit-based QKD systems using a weak coherent state source and
decoy states. Specifically, by implementing a linear-optics
unambiguous-state-discrimination measurement, we show that the security of a
system without phase randomization --- which is a step assumed in conventional
security analyses but sometimes neglected in practice --- can be compromised.
We conclude that implementing phase randomization is essential to the security
of decoy-state QKD systems under current security analyses.Comment: 12 pages, 5 figure
4-EthÂoxy-N′-propanoylpyridine-2-carbohydrazide
In the crystal structure of the title compound, C11H15N3O3, molÂecules are linked into a chain by interÂmolecular N—H⋯O hydrogen bonds
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