119 research outputs found
Electron correlation and Fermi surface topology of NaCoO
The electronic structure of NaCoO revealed by recent photoemission
experiments shows important deviations from band theory predictions. The six
small Fermi surface pockets predicted by LDA calculations have not been
observed as the associated band fails to cross the Fermi level for
a wide range of sodium doping concentration . In addition, significant
bandwidth renormalizations of the complex have been observed. We show
that these discrepancies are due to strong electronic correlations by studying
the multi-orbital Hubbard model in the Hartree-Fock and strong-coupling
Gutzwiller approximation. The quasiparticle dispersion and the Fermi surface
topology obtained in the presence of strong local Coulomb repulsion are in good
agreement with experiments.Comment: 5 pages, 4 figures, revtex4; minor changes, to be published in Phys.
Rev. Let
Multi-Resource Allocation for On-Device Distributed Federated Learning Systems
This work poses a distributed multi-resource allocation scheme for minimizing
the weighted sum of latency and energy consumption in the on-device distributed
federated learning (FL) system. Each mobile device in the system engages the
model training process within the specified area and allocates its computation
and communication resources for deriving and uploading parameters,
respectively, to minimize the objective of system subject to the
computation/communication budget and a target latency requirement. In
particular, mobile devices are connect via wireless TCP/IP architectures.
Exploiting the optimization problem structure, the problem can be decomposed to
two convex sub-problems. Drawing on the Lagrangian dual and harmony search
techniques, we characterize the global optimal solution by the closed-form
solutions to all sub-problems, which give qualitative insights to
multi-resource tradeoff. Numerical simulations are used to validate the
analysis and assess the performance of the proposed algorithm
Atomic-Scale Strain Manipulation of a Charge Density Wave
A charge density wave (CDW) is one of the fundamental instabilities of the
Fermi surface occurring in a wide range of quantum materials. In dimensions
higher than one, where Fermi surface nesting can play only a limited role, the
selection of the particular wave vector and geometry of an emerging CDW should
in principle be susceptible to controllable manipulation. In this work, we
implement a simple method for straining materials compatible with
low-temperature scanning tunneling microscopy/spectroscopy (STM/S), and use it
to strain-engineer new CDWs in 2H-NbSe2. Our STM/S measurements combined with
theory reveal how small strain-induced changes in the electronic band structure
and phonon dispersion lead to dramatic changes in the CDW ordering wave vector
and geometry. Our work unveils the microscopic mechanism of a CDW formation in
this system, and can serve as a general tool compatible with a range of
spectroscopic techniques to engineer novel electronic states in any material
where local strain or lattice symmetry breaking plays a role.Comment: to appear in PNAS (2018
Comparison of the Effects of Acarbose and TZQ-F, a New Kind of Traditional Chinese Medicine to Treat Diabetes, Chinese Healthy Volunteers
Ethnopharmacological Relevance. TZQ-F has been traditionally used in Traditional Chinese Medicine as a formula for the treatment of diabetes. Aim of the Study. This study aims to compare the pharmacologic effects and gastrointestinal adverse events between TZQ-F and acarbose. Methods. The double-blind randomized placebo-controlled fivefold crossover study was performed in 20 healthy male volunteers. Plasma glucose, plasma IRI, and plasma C-peptide were measured to assess the pharmacologic effects. Flatus and bowel activity were measured to assess the adverse event of gastrointestinal effect. Results. 3 and 4 tablets of TZQ decreased the Cmax of plasma glucose compared with that of the previous day and with placebo. 3 tablets also decreased Cmax of plasma C-peptide compared with placebo. 4 tablets increased Cmax of plasma insulin after breakfast and the AUC of plasma C-peptide after breakfast and dinner. 2 tablets did not decrease plasma glucose and elevated the Cmax and AUC of C-peptide after breakfast and dinner, respectively. Acarbose 50 mg decreased the Cmax of plasma insulin and C-peptide after breakfast and the Cmax of plasma glucose and C-peptide after dinner. The subjects who received TZQ did not report any abdominal adverse events. Conclusions. 3 tablets of TZQ have the same effects as the acarbose
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Patterning-Induced Ferromagnetism of Fe3GeTe2 van der Waals Materials beyond Room Temperature.
Magnetic van der Waals (vdW) materials have emerged as promising candidates for spintronics applications, especially after the recent discovery of intrinsic ferromagnetism in monolayer vdW materials. There has been a critical need for tunable ferromagnetic vdW materials beyond room temperature. Here, we report a real-space imaging study of itinerant ferromagnet Fe3GeTe2 and the enhancement of its Curie temperature well above ambient temperature. We find that the magnetic long-range order in Fe3GeTe2 is characterized by an unconventional out-of-plane stripe-domain phase. In Fe3GeTe2 microstructures patterned by a focused ion beam, the out-of-plane stripe domain phase undergoes a surprising transition at 230 K to an in-plane vortex phase that persists beyond room temperature. The discovery of tunable ferromagnetism in Fe3GeTe2 materials opens up vast opportunities for utilizing vdW magnets in room-temperature spintronics devices
Baseline model based structural health monitoring method under varying environment
Environment has significant impacts on the structure performance and will change features of sensor measurements on the monitored structure. The effect of varying environment needs to be considered and eliminated while conducting structural health monitoring. In order to achieve this purpose, a baseline model based structural health monitoring method is proposed in this paper. The relationship between signal features and varying environment, known as a baseline model, is first established. Then, a tolerance range of the signal feature is evaluated via a data based statistical analysis. Furthermore, the health indicator, which is defined as the proportion of signal features within the tolerance range, is used to judge whether the structural system is in normal working condition or not so as to implement the structural health monitoring. Finally, experimental data analysis for an operating wind turbine is conducted and the results demonstrate the performance of the proposed new technique
The multidrug-resistant Pseudomonas fluorescens strain: a hidden threat in boar semen preservation
Although the bacterial composition of boar ejaculate has been extensively studied, the bacterial composition of extended boar semen is often overlooked, despite the potential risks these microorganisms may pose to the long-term preservation of extended boar semen at 15–17°C. In this study, we characterized the bacterial community composition of extended semen and discovered that Pseudomonas spp. was the dominant flora. The dominant strains were further isolated and identified as a potential new species in the Pseudomonas fluorescens group and named GXZC strain, which had adverse effects on sperm quality and was better adapted to growth at 17°C. Antimicrobial susceptibility testing showed that the GXZC strain was resistant to all commonly used veterinary antibiotics. Whole-genome sequencing (WGS) and genome annotation revealed the large genetic structure and function [7,253,751 base pairs and 6,790 coding sequences (CDSs)]. Comparative genomic analysis with the closest type strains showed that the GXZC strain predicted more diversity of intrinsic and acquired resistance genes to multi-antimicrobial agents. Taken together, our study highlights a problem associated with the long-term storage of extended boar semen caused by a P. fluorescens group strain with unique biological characteristics. It is essential to develop a new antibacterial solution for the long-term preservation of boar semen
Superconductivity and orbital-selective nematic order in a new titanium-based kagome metal CsTi3Bi5
Fabrication of new types of superconductors with novel physical properties
has always been a major thread in the research of superconducting materials. An
example is the enormous interests generated by the cascade of correlated
topological quantum states in the newly discovered vanadium-based kagome
superconductors AV3Sb5 (A=K, Rb, and Cs) with a Z2 topological band structure.
Here we report the successful fabrication of single-crystals of titanium-based
kagome metal CsTi3Bi5 and the observation of superconductivity and electronic
nematicity. The onset of the superconducting transition temperature Tc is
around 4.8 K. In sharp contrast to the charge density wave superconductor
AV3Sb5, we find that the kagome superconductor CsTi3Bi5 preserves translation
symmetry, but breaks rotational symmetry and exhibits an electronic nematicity.
The angular-dependent magnetoresistivity shows a remarkable two-fold rotational
symmetry as the magnetic field rotates in the kagome plane. The scanning
tunneling microscopy and spectroscopic imaging detect rotational-symmetry
breaking C2 quasiparticle interference patterns (QPI) at low energies,
providing further microscopic evidence for electronic nematicity. Combined with
first-principle calculations, we find that the nematic QPI is orbital-selective
and dominated by the Ti dxz and dyz orbitals, possibly originating from the
intriguing orbital bond nematic order. Our findings in the new "135" material
CsTi3Bi5 provide new directions for exploring the multi-orbital correlation
effect and the role of orbital or bond order in the electron liquid crystal
phases evidenced by the symmetry breaking states in kagome superconductors
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