Designer Topological Insulators in Superlattices

Gapless Dirac surface states are protected at the interface of topological and normal band insulators. In a binary superlattice bearing such interfaces, we establish that valley-dependent dimerization of symmetry-unrelated Dirac surface states can be exploited to induce topological quantum phase transitions. This mechanism leads to a rich phase diagram that allows us to design strong, weak, and crystalline topological insulators. Our ab initio simulations further demonstrate this mechanism in [111] and [110] superlattices of calcium and tin tellurides.Comment: 5 pages, 4 figure

Giant and tunable valley degeneracy splitting in MoTe2

Monolayer transition-metal dichalcogenides possess a pair of degenerate helical valleys in the band structure that exhibit fascinating optical valley polarization. Optical valley polarization, however, is limited by carrier lifetimes of these materials. Lifting the valley degeneracy is therefore an attractive route for achieving valley polarization. It is very challenging to achieve appreciable valley degeneracy splitting with applied magnetic field. We propose a strategy to create giant splitting of the valley degeneracy by proximity-induced Zeeman effect. As a demonstration, our first principles calculations of monolayer MoTe$_2$ on a EuO substrate show that valley splitting over 300 meV can be generated. The proximity coupling also makes interband transition energies valley dependent, enabling valley selection by optical frequency tuning in addition to circular polarization. The valley splitting in the heterostructure is also continuously tunable by rotating substrate magnetization. The giant and tunable valley splitting adds a readily accessible dimension to the valley-spin physics with rich and interesting experimental consequences, and offers a practical avenue for exploring device paradigms based on the intrinsic degrees of freedom of electrons.Comment: 8 pages, 5 figures, 1 tabl

Coupling the valley degree of freedom to antiferromagnetic order

Conventional electronics are based invariably on the intrinsic degrees of freedom of an electron, namely, its charge and spin. The exploration of novel electronic degrees of freedom has important implications in both basic quantum physics and advanced information technology. Valley as a new electronic degree of freedom has received considerable attention in recent years. In this paper, we develop the theory of spin and valley physics of an antiferromagnetic honeycomb lattice. We show that by coupling the valley degree of freedom to antiferromagnetic order, there is an emergent electronic degree of freedom characterized by the product of spin and valley indices, which leads to spin-valley dependent optical selection rule and Berry curvature-induced topological quantum transport. These properties will enable optical polarization in the spin-valley space, and electrical detection/manipulation through the induced spin, valley and charge fluxes. The domain walls of an antiferromagnetic honeycomb lattice harbors valley-protected edge states that support spin-dependent transport. Finally, we employ first principles calculations to show that the proposed optoelectronic properties can be realized in antiferromagnetic manganese chalcogenophosphates (MnPX_3, X = S, Se) in monolayer form.Comment: 6 pages, 5 figure

Dependence of the decoherence of polarization states in phase-damping channels on the frequency spectrum envelope of photons

We consider the decoherence of photons suffering in phase-damping channels. By exploring the evolutions of single-photon polarization states and two-photon polarization-entangled states, we find that different frequency spectrum envelopes of photons induce different decoherence processes. A white frequency spectrum can lead the decoherence to an ideal Markovian process. Some color frequency spectrums can induce asymptotical decoherence, while, some other color frequency spectrums can make coherence vanish periodically with variable revival amplitudes. These behaviors result from the non-Markovian effects on the decoherence process, which may give rise to a revival of coherence after complete decoherence.Comment: 7 pages, 4 figures, new results added, replaced by accepted versio

骨科择期手术患者压疮危险因素的研究

Objectives：The purposes of the study were to investigate the incidence of pressure ulcer of orthopedics patients undergoing selective operation, and to identify the risk factors of pressure ulcer.Methods: A prospective cohort study was employed in this study. Data were collected concerning the general characteristics as well as preoperative, intraoperative and postoperative indicators probable to induce pressure ulcer and then analyzed in view of the risk factors of pressure ulcer. Results: (1) Pressure ulcers developed in thirty five patients (10.1%) on day 0 and the first 3 days following surgery; (2) age, hemoglobin, lymphocyte and getting up late for the first time after surgery were significantly associated with the occurrence of pressure ulcers (odds ratio 1.068,  0.948, 0.293, 1.019, respectively).Conclusions: (1) Patients have higher risk of developing pressure ulcer after operation, the critical period beginning from the operation day to the 3rd day after operation. (2) The age older, the later getting up for the first time after surgery, the liable it is for the patients to develop pressure ulcer postoperatively.目的 调查骨科择期手术后患者压疮的发生率，分析术后压疮发生的危险因素。方法 采用前瞻性队列研究的方法，样本采用便利取样。记录患者的一般资料、术前、术中和术后可能与压疮发生有一定关系的各项指标，对骨科手术后患者的压疮危险因素进行分析。结果 （1）共35例患者发生了压疮，发生率为10.1%；术后皮肤出现异常的时间均在手术当天至手术后1～3天内；（2）高龄、术前低淋巴细胞总数、术前低血红蛋白含量和术后首次下地时间晚是骨科择期手术后患者发生压疮的危险因素，OR值分别为1.068、0.948、0.293、1.019。结论 （1）骨科择期手术后患者是院内压疮发生的高危人群，其中手术当天至手术后第3天为术后压疮预防的关键时期；（2）年龄越大、术前血红蛋白含量、淋巴细胞总数水平越低及手术后首次下地时间越晚，术后发生压疮的可能性就越大

Pathological Evidence Exploration in Deep Retinal Image Diagnosis

Though deep learning has shown successful performance in classifying the label and severity stage of certain disease, most of them give few evidence on how to make prediction. Here, we propose to exploit the interpretability of deep learning application in medical diagnosis. Inspired by Koch's Postulates, a well-known strategy in medical research to identify the property of pathogen, we define a pathological descriptor that can be extracted from the activated neurons of a diabetic retinopathy detector. To visualize the symptom and feature encoded in this descriptor, we propose a GAN based method to synthesize pathological retinal image given the descriptor and a binary vessel segmentation. Besides, with this descriptor, we can arbitrarily manipulate the position and quantity of lesions. As verified by a panel of 5 licensed ophthalmologists, our synthesized images carry the symptoms that are directly related to diabetic retinopathy diagnosis. The panel survey also shows that our generated images is both qualitatively and quantitatively superior to existing methods.Comment: to appear in AAAI (2019). The first two authors contributed equally to the paper. Corresponding Author: Feng L

Sino-European Transcontinental Basic and Clinical High-Tech Acupuncture Studies—Part 2: Acute Stimulation Effects on Heart Rate and Its Variability in Patients with Insomnia

This second part of a series of Sino-European high-tech acupuncture studies describes the first clinical transcontinental teleacupuncture measurements in patients with insomnia. Heart rate (HR) and heart rate variability (HRV) measurements in 28 patients (mean age ± SD: 41.9 ± 14.6 years) were performed under standardized conditions in Harbin, China, and the data analysis was performed in Graz, Austria. Similar to the first part of the series, the electrocardiograms (ECGs) were recorded by an HRV Medilog AR12 system during acupuncture of the Shenmen point (HT7) on the left hand. HR decreased significantly (P < 0.001) during and after acupuncture stimulation of the HT7 acupuncture point. Total HRV increased significantly (P < 0.05) immediately after acupuncture stimulation, but there was no long-lasting effect. The values of the low-frequency (LF) and high-frequency (HF) band increased significantly after the stimulation compared to baseline values; however, the LF/HF ratio showed no significant changes. Together with the results of previous studies, the present results can serve as a solid basis for further development of acupressure or acupuncture stimulation equipment for complementary use in treating insomnia