Direct observation of topological magnon polarons in a multiferroic material.

Magnon polarons are novel elementary excitations possessing hybrid magnonic and phononic signatures, and are responsible for many exotic spintronic and magnonic phenomena. Despite long-term sustained experimental efforts in chasing for magnon polarons, direct spectroscopic evidence of their existence is hardly observed. Here, we report the direct observation of magnon polarons using neutron spectroscopy on a multiferroic Fe2Mo3O8 possessing strong magnon-phonon coupling. Specifically, below the magnetic ordering temperature, a gap opens at the nominal intersection of the original magnon and phonon bands, leading to two separated magnon-polaron bands. Each of the bands undergoes mixing, interconverting and reversing between its magnonic and phononic components. We attribute the formation of magnon polarons to the strong magnon-phonon coupling induced by Dzyaloshinskii-Moriya interaction. Intriguingly, we find that the band-inverted magnon polarons are topologically nontrivial. These results uncover exotic elementary excitations arising from the magnon-phonon coupling, and offer a new route to topological states by considering hybridizations between different types of fundamental excitations.

Inducing itinerant ferromagnetism by manipulating van Hove singularity in epitaxial monolayer 1T-VSe2.

The itinerant ferromagnetism can be induced by a van Hove singularity (VHS) with a divergent density of states at Fermi level. Utilizing the giant magnified dielectric constant εr of SrTiO3(111) substrate with cooling, here we successfully manipulated the VHS in the epitaxial monolayer (ML) 1T-VSe2 film approaching to Fermi level via the large interfacial charge transfer, and thus induced a two-dimensional (2D) itinerant ferromagnetic state below 3.3 K. Combining the direct characterization of the VHS structure via angle-resolved photoemission spectroscopy (ARPES), together with the theoretical analysis, we ascribe the manipulation of VHS to the physical origin of the itinerant ferromagnetic state in ML 1T-VSe2. Therefore, we further demonstrated that the ferromagnetic state in the 2D system can be controlled through manipulating the VHS by engineering the film thickness or replacing the substrate. Our findings clearly evidence that the VHS can serve as an effective manipulating degree of freedom for the itinerant ferromagnetic state, expanding the application potentials of 2D magnets for the next-generation information technology.

Discovery of coexisting Dirac and triply degenerate magnons in a three-dimensional antiferromagnet.

Topological magnons are emergent quantum spin excitations featured by magnon bands crossing linearly at the points dubbed nodes, analogous to fermions in topological electronic systems. Experimental realisation of topological magnons in three dimensions has not been reported so far. Here, by measuring spin excitations (magnons) of a three-dimensional antiferromagnet Cu3TeO6 with inelastic neutron scattering, we provide direct spectroscopic evidence for the coexistence of symmetry-protected Dirac and triply degenerate nodes, the latter involving three-component magnons beyond the Dirac-Weyl framework. Our theoretical calculations show that the observed topological magnon band structure can be well described by the linear-spin-wave theory based on a Hamiltonian dominated by the nearest-neighbour exchange interaction J1. As such, we showcase Cu3TeO6 as an example system where Dirac and triply degenerate magnonic nodal excitations coexist, demonstrate an exotic topological state of matter, and provide a fresh ground to explore the topological properties in quantum materials.

Spin-Glass Ground State in a Triangular-Lattice Compound YbZnGaO_{4}.

We report on comprehensive results identifying the ground state of a triangular-lattice structured YbZnGaO_{4} as a spin glass, including no long-range magnetic order, prominent broad excitation continua, and the absence of magnetic thermal conductivity. More crucially, from the ultralow-temperature ac susceptibility measurements, we unambiguously observe frequency-dependent peaks around 0.1 K, indicating the spin-glass ground state. We suggest this conclusion holds also for its sister compound YbMgGaO_{4}, which is confirmed by the observation of spin freezing at low temperatures. We consider disorder and frustration to be the main driving force for the spin-glass phase.

Comamonas kerstersii bacteremia in a patient with acute perforated appendicitis: A rare case report.

RATIONALE: Comamonas species are rarely associated with human infections. Recent reports found that Comamonas kerstersii was associated with severe diseases such as abdominal infection and bacteremia. However, C. kerstersii maybe be confused with Comamonas testosteroni using the automatic bacterial identification systems currently available. PATIENT CONCERNS: A 31-year-old man who had onset of left upper abdominal pain developed clinical manifestations of right lower abdominal pain and classic migration of pain at the temperature of 39°C. The positive strain of aerobic and anaerobic bottles of blood cultures was identified. DIAGNOSES: The patient was diagnosed as acute peritonitis and perforated appendix with abdominal abscess. INTERVENTIONS: The bacterium was identified by routine methods, MALDI-TOF-MS and PCR amplification of the 16S rRNA. The patient was treated with exploratory laparotomy, appendectomy, tube drainage, and prescribing antibiotic treatment. OUTCOMES: The patients were discharged with complete recovery. The organisms were confirmed as C. kerstersii by MALDI-TOF-MS and a combination of the other results. LESSONS: Our findings suggest that C. kerstersii infection occurs most often in association with perforated appendix and bacteremia. We presume that C. kerstersii is an opportunistic pathogen or commensal with the digestive tract and appendix bacteria.

Spin-Wave Excitations Evidencing the Kitaev Interaction in Single Crystalline α-RuCl_{3}.

Kitaev interactions underlying a quantum spin liquid have long been sought, but experimental data from which their strengths can be determined directly, are still lacking. Here, by carrying out inelastic neutron scattering measurements on high-quality single crystals of α-RuCl_{3}, we observe spin-wave spectra with a gap of ∼2 meV around the M point of the two-dimensional Brillouin zone. We derive an effective-spin model in the strong-coupling limit based on energy bands obtained from first-principles calculations, and find that the anisotropic Kitaev interaction K term and the isotropic antiferromagnetic off-diagonal exchange interaction Γ term are significantly larger than the Heisenberg exchange coupling J term. Our experimental data can be well fit using an effective-spin model with K=-6.8 meV and Γ=9.5 meV. These results demonstrate explicitly that Kitaev physics is realized in real materials.

Assessing Short-Term Voltage Stability of Electric Power Systems by a Hierarchical Intelligent System.

In the smart grid paradigm, growing integration of large-scale intermittent renewable energies has introduced significant uncertainties to the operations of an electric power system. This makes real-time dynamic security assessment (DSA) a necessity to enable enhanced situational-awareness against the risk of blackouts. Conventional DSA methods are mainly based on the time-domain simulation, which are insufficiently fast and knowledge-poor. In recent years, the intelligent system (IS) strategy has been identified as a promising approach to facilitate real-time DSA. While previous works mainly concentrate on the rotor angle stability, this paper focuses on another yet increasingly important dynamic insecurity phenomenon-the short-term voltage instability, which involves fast and complex load dynamics. The problem is modeled as a classification subproblem for transient voltage collapse and a prediction subproblem for unacceptable dynamic voltage deviation. A hierarchical IS is developed to address the two subproblems sequentially. The IS is based on ensemble learning of random-weights neural networks and is implemented in an offline training, a real-time application, and an online updating pattern. The simulation results on the New England 39-bus system verify its superiority in both learning speed and accuracy over some state-of-the-art learning algorithms.

Robust Kernel Low-Rank Representation.

Recently, low-rank representation (LRR) has shown promising performance in many real-world applications such as face clustering. However, LRR may not achieve satisfactory results when dealing with the data from nonlinear subspaces, since it is originally designed to handle the data from linear subspaces in the input space. Meanwhile, the kernel-based methods deal with the nonlinear data by mapping it from the original input space to a new feature space through a kernel-induced mapping. To effectively cope with the nonlinear data, we first propose the kernelized version of LRR in the clean data case. We also present a closed-form solution for the resultant optimization problem. Moreover, to handle corrupted data, we propose the robust kernel LRR (RKLRR) approach, and develop an efficient optimization algorithm to solve it based on the alternating direction method. In particular, we show that both the subproblems in our optimization algorithm can be efficiently and exactly solved, and it is guaranteed to obtain a globally optimal solution. Besides, our proposed algorithm can also solve the original LRR problem, which is a special case of our RKLRR when using the linear kernel. In addition, based on our new optimization technique, the kernelization of some variants of LRR can be similarly achieved. Comprehensive experiments on synthetic data sets and real-world data sets clearly demonstrate the efficiency of our algorithm, as well as the effectiveness of RKLRR and the kernelization of two variants of LRR.

Face recognition with multi-resolution spectral feature images.

The one-sample-per-person problem has become an active research topic for face recognition in recent years because of its challenges and significance for real-world applications. However, achieving relatively higher recognition accuracy is still a difficult problem due to, usually, too few training samples being available and variations of illumination and expression. To alleviate the negative effects caused by these unfavorable factors, in this paper we propose a more accurate spectral feature image-based 2DLDA (two-dimensional linear discriminant analysis) ensemble algorithm for face recognition, with one sample image per person. In our algorithm, multi-resolution spectral feature images are constructed to represent the face images; this can greatly enlarge the training set. The proposed method is inspired by our finding that, among these spectral feature images, features extracted from some orientations and scales using 2DLDA are not sensitive to variations of illumination and expression. In order to maintain the positive characteristics of these filters and to make correct category assignments, the strategy of classifier committee learning (CCL) is designed to combine the results obtained from different spectral feature images. Using the above strategies, the negative effects caused by those unfavorable factors can be alleviated efficiently in face recognition. Experimental results on the standard databases demonstrate the feasibility and efficiency of the proposed method.

The comparisive study of the clinical effect of rotary self-locking intramedullary nail and intramedullary interlocking nail for the treatment of femur fracture / 中国骨伤

<p><b>OBJECTIVE</b>To compare the clinical effect of rotary self-locking intramedullary nail (RSIN) and intramedullary interlocking nail (IIN) for the treatment of fresh femoral shaft fracture.</p><p><b>METHODS</b>The radiological records of 60 fresh femoral shaft fractures (41 stable fractures and 19 unstable fractures) were retrospectively analyzed. Among them, 49 were male and 11 were female. The average age was 33.5 years old (range from 12 to 68 years old). All cases were fresh fracture with no important blood vessel or nerve injury, which were taken operation with RSIN on IIN respectively in 2 h-7 d after injury. The patients in IIN group began functional movements at postoperative 4 to 5 days and could bear the weight of 10-15 kg. The patients in RSIN group could began functional exercises after the wound healed and bear partly weight after 6 weeks. Both groups were contrasted on the biomechanics, operation procedure, fracture healing time, functional recovery and operative indication.</p><p><b>RESULTS</b>Both groups were followed-up for average 13 months. IIN group: the average healing time of closed femur fracture was 16 weeks while that of open fracture was 20 weeks. The healing rate was 100% and the malunion rate was 7.9%. The excellent and good rate of functional recovery was 93.3% including excellent in 27 cases, good in 1, fair in 1 and bad in 1. RSIN group: the average healing time of closed femur fracture was 16 weeks while open fracture was 23 weeks. The healing rate was 87% and the malunion rate was 18.2%. The excellent and good rate of functional recovery was 83.3% including excellent in 23 cases, good in 2, fair in 3 and bad in 2. No implant break and nonunion happened. The differences between two groups in healing time, deformity-union rate and the rate of the twice operation were statistically significant.</p><p><b>CONCLUSION</b>IIN provides a reliable and practical alternative method for the treatment of all kinds of femoral shaft fracture and its important complication is fewer than RSIN group. RSIN also has a good curative effect in its own indication.</p>

[Experimental study of the transferred keratinocytes transplanted on biomembrane].

OBJECTIVE: To search an ideal carrier of transferred keratinocytes for transplantation. METHODS: The transferred keratinocytes were seeded on the surfaces of the artificial dermis and the silicone membrane and cultured in vitro for 2 weeks. The growth of the keratinocytes was observed by microscope and scanning electron microscope. RESULTS: The keratinocytes implanted on the artificial dermis began to rupture and died after 2 to 3 days. While the keratinocytes adhered well on the surface of silicone membrane with pseudopodia formation after 1 week under scanning electron microscope, and the cells kept normal morphological and proliferative properties 2 weeks later. CONCLUSION: The silicone membrane can be applied as an useful carrier for the keratinocytes transplantation.