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The strain coupling of misfit dislocations and ferroelastic domains is revealed in [101]-oriented PbTiO3/(La, Sr)(Al, Ta)O3 films and flexoelectric-induced polarization rotation is observed around the misfit dislocation cores.

Observation of high energy and very high emission from Gamma Ray Bursts (GRBs) is crucial to study the gigantic explosion and the underline processes. With a large field-of-view and almost full duty cycle, the Water Cherenkov Detector Array (WCDA), a sub-array of the Large High Altitude Air Shower Observatory (LHAASO), is appropriate to monitor the very high energy emission from unpredictable transients such as GRBs. Nevertheless, the main issue for an extensive air shower array is the high energy threshold which limits the horizon of the detector. To address this issue a new trigger method is developed in this article to lower the energy threshold of WCDA for GRB observation. The proposed method significantly improves the detection efficiency of WCDA for gamma-rays around the GRB direction at 10-300 GeV. The sensitivity of the WCDA for GRB detection with the new trigger method is estimated. The achieved sensitivity of the quarter WCDA array above 10 GeV is comparable with that of Fermi-LAT. The data analysis process and corresponding fluence upper limit for GRB 190719C is presented as an example.

When expressing streptavidin recombinant polypeptide on magnetosomes (called bacterial magnetic nanoparticles, or BMPs), the presence of endogenous bacterial biotin might be detrimental. In the study, the streptavidin monomer fragment (SA1–116) was fused with the intein N-terminal (termed precursor SA1–116-IN), and SA1–116-IN was expressed in E. coli (BL21). Meanwhile, the SA117–160 fragment was fused with the C-terminal intein, and then this chimeric polypeptide was expressed on magnetosomes by fusion with magnetosome membrance protein MamF. In the in vitro protein splicing system, the purified engineered magnetosomes (BMP-SA117–160-IC) and the SA1–116-IN precursor were mixed. Intein-mediated trans-splicing reaction was induced to produce the functional magnetic beads BMP-SA. Our results indicate that intein-mediated protein trans-splicing may lead to efficient synthesis of the recombinant streptavidin on the magnetosomes, showing its promising potential to produce other functional magnetic nanoparticles.

The main scientific goal of LHAASO-WCDA is to survey gamma-ray sources with energy from 100 GeV to 30 TeV. To observe high-energy shower events, especially to measure the energy spectrum of cosmic rays from 100 TeV to 10 PeV, a dynamic range extension system (WCDA++) is designed to use a 1.5-inch PMT with a dynamic range of four orders of magnitude for each cell in WCDA-1. The dynamic range is extended by using these PMTs to measure the effective charge density in the core region of air shower events, which is an important parameter for identifying the composition of primary particles. The system has been running for more than one year. In this paper, the details of the design and performance of WCDA++ are presented.

The kilometer square array (KM2A) of the large high altitude air shower observatory (LHAASO) aims at surveying the northern γ-ray sky at energies above 10 TeV with unprecedented sensitivity. γ-ray observations have long been one of the most powerful tools for dark matter searches, as, e.g., high-energy γ rays could be produced by the decays of heavy dark matter particles. In this Letter, we present the first dark matter analysis with LHAASO-KM2A, using the first 340 days of data from 1/2-KM2A and 230 days of data from 3/4-KM2A. Several regions of interest are used to search for a signal and account for the residual cosmic-ray background after γ/hadron separation. We find no excess of dark matter signals, and thus place some of the strongest γ-ray constraints on the lifetime of heavy dark matter particles with mass between 105 and 109 GeV. Our results with LHAASO are robust, and have important implications for dark matter interpretations of the diffuse astrophysical high-energy neutrino emission.

The aim of this study was to investigate the preventive effect of pancreatic duct stent on acute pancreatitis after endoscopic retrograde cholangiopancreatography. A retrospective analysis of the case data of patients who first underwent endoscopic retrograde cholangiopancreatography for choledocholithiasis in the Beijing Friendship Hospital from January 2015 to December 2019 for 5 years. According to whether the pancreatic duct stent was indwelled during the operation, they were divided into pancreatic duct stent group (147 cases) and non-indwelling pancreatic duct stent group (192 cases). The incidence of acute pancreatitis after endoscopic retrograde cholangiopancreatography was compared between the two groups according to COTTON criteria. Independent sample为探讨胰管支架对内镜逆行性胰胆管造影（ERCP）术后预防急性胰腺炎（PEP）发生的作用，本研究回顾性分析2015年1月至2019年12月期间在首都医科大学附属北京友谊医院因胆总管结石首次行内镜逆行胰胆管造影患者的病例资料。根据术中是否留置胰管支架分为胰管支架组（147例）和未留置胰管支架组（192例）。以COTTON标准诊断是否发生内镜逆行性胰胆管造影术后急性胰腺炎，比较两组间急性胰腺炎的发生率。采用独立样本

Train-induced resonance of a railway bridge occurs when the train speed coincides with the primary resonance speed ([Formula: see text]) of the bridge, from which we can determine the sub-resonance speed as ([Formula: see text]). The primary resonance speed of a short bridge is generally much higher than the operation speeds of current high-speed trains but the corresponding sub-resonance speeds probably lie in the operation speed range. Such a resonance scenario can be observed from the vibration of a double-track bridge subjected to an eccentrically moving train, in which the deck vibration is combined by the vertical-flexural and torsional vibration modes of the bridge. Once the two modal sub-resonance speeds coincide with each other, a double sub-resonance will be developed on the bridge. In this study, an iteration-based train–bridge interaction finite element procedure will be presented to demonstrate the double resonance phenomenon. As expected, the double resonance may bring about a dramatic amplification on deck vibration. Such an excessive vibration is harmful to ballast stability and track maintenance of railway bridges.

The extension of the cosmic-ray spectrum beyond 1 petaelectronvolt (PeV; 1015 electronvolts) indicates the existence of the so-called PeVatrons—cosmic-ray factories that accelerate particles to PeV energies. We need to locate and identify such objects to find the origin of Galactic cosmic rays1. The principal signature of both electron and proton PeVatrons is ultrahigh-energy (exceeding 100 TeV) γ radiation. Evidence of the presence of a proton PeVatron has been found in the Galactic Centre, according to the detection of a hard-spectrum radiation extending to 0.04 PeV (ref. 2). Although γ-rays with energies slightly higher than 0.1 PeV have been reported from a few objects in the Galactic plane3–6, unbiased identification and in-depth exploration of PeVatrons requires detection of γ-rays with energies well above 0.1 PeV. Here we report the detection of more than 530 photons at energies above 100 teraelectronvolts and up to 1.4 PeV from 12 ultrahigh-energy γ-ray sources with a statistical significance greater than seven standard deviations. Despite having several potential counterparts in their proximity, including pulsar wind nebulae, supernova remnants and star-forming regions, the PeVatrons responsible for the ultrahigh-energy γ-rays have not yet been firmly localized and identified (except for the Crab Nebula), leaving open the origin of these extreme accelerators. Observations of γ-rays with energies up to 1.4 PeV find that 12 sources in the Galaxy are PeVatrons, one of which is the Crab Nebula.

上气道高反应性（upper airway hyperresponsiveness，AHR）疾病主要包括变应性鼻炎、血管运动性鼻炎、局部变应性鼻炎、非变应性鼻炎伴嗜酸细胞增多综合征等，是一类高度异质性疾病，发病率高，发病机制复杂。除了传统的免疫学理论外，还存在神经免疫机制。本文主要介绍神经免疫的基本概念和研究进展；AHR时神经免疫的主要形式，如神经源性炎性反应，2型固有淋巴细胞诱导的Th2样反应等；瞬时受体电位及其在冷热刺激诱发神经源性炎性反应和免疫源性炎性反应中的作用机制；生物钟紊乱及其对外周靶器官生物时相的影响；最后结合翼管神经切断术介绍神经阻断在神经免疫调控中的作用。.

Patients with dental problems may suffer from various systemic diseases at the same time. The concomitant systemic diseases can have impacts and risks on the diagnosis, treatment planning and therapeutic practice in dentistry. The author briefly expounds the influences of systemic diseases on dental diagnosis and treatment and the prevention of risks from seven aspects: cardio-cerebral vascular system, blood system, respiratory system, endocrine system, digestive system, genitourinary system, nervous system and mental system, in order to provide references for the dental clinicians.患有口腔疾病者可能同时患有不同程度的全身系统性疾病，这些伴发的系统性疾病对口腔疾病的诊疗时机、方案制订等带来影响和风险。本文从心脑血管系统、血液系统、呼吸系统、内分泌系统、消化系统、泌尿生殖系统、神经及精神系统7个方面简要阐述了系统性疾病对口腔诊疗的影响以及风险防范，以期为临床提供参考。.

患儿 男，11岁，因“急性髂骨骨髓炎”于2020年1月入住山东第一医科大学附属省立医院小儿骨科，手术后出现呼吸困难急转入小儿重症医学科，因体循环高压行超声心动图检查发现肺动脉高压，进一步行心脏大血管CT造影（CTA）发现右下肺动脉栓塞，给予积极抗感染，依诺肝素皮下注射及口服利伐沙班序贯抗凝治疗，1个月后复查CTA示肺栓塞消失，随访1年患儿恢复良好。儿童急性骨髓炎合并肺栓塞临床特征不典型，临床上极易误诊，临床医师亟需提高对该病的认知和诊疗水平。.

OBJECTIVE: To compare the clinical effect of microsurgery and endovascular embolization in the treatment of spinal dural arteriovenous fistula (SDAVF) by meta-analysis. METHODS: A systematic review was performed to retrieve all relevant literature about surgical treatment or endovascular embolization of SDAVF up to December 2019 through PubMed, Embase, Web of Science, Cochrane Central Register of Controlled Trials Results, CNKI, Wanfang Data, and SinoMed. The Chinese and English key words included: "SDAVF", "spinal dural arteriovenous fistula", "spinal AVM", "spinal vascular malformation and treatment". The included studies were evaluated using the Newcastle-Ottawa scale. The early failure rate, long-term recurrence, neurological recovery, and complications were evaluated and the clinical effects of the two methods in the treatment of SDAVF were compared by using RevMan 5.3 software. And a further subgroup analysis of the therapeutic effect of endovascular embolization with different embolic agents was conducted. RESULTS: A total of 46 studies involving 1 958 cases of SDAVF were included, in which 935 cases were treated by microsurgery and 1 023 cases were treated by endovascular embolization. The funnel plot demonstrated that there was no publication bias. The results of meta-analysis showed that the incidence of early surgical failure was lower than that of endovascular embolization (OR=0.20, 95%CI: 0.13-0.30, P < 0.05), and the long-term recurrence was also lower than that of endovascular embolization (OR=0.36, 95%CI: 0.22-0.58, P < 0.05). The improvement of neurological function in the surgical patients is significantly higher than that in the patients treated with endovascular embolization (OR=2.86, 95%CI: 1.36-5.99, P < 0.05). There was no significant difference in the occurrence of complications in these two groups (OR=1.52, 95%CI: 0.88-2.64, P=0.14). In the cases of endovascular embolization, the risk of treatment failure or recurrence was higher with Onyx glue than with n-butyl 2-cyanoacrylate (NBCA), and the difference was statistically significant (OR=4.70, 95%CI: 1.55-14.28, P < 0.05). CONCLUSION: Although the treatment of dural arteriovenous fistulas by intravascular embolization has been widely used, the clinical effect of microsurgery is still better than that of endovascular embolization. Large scale and high-quality randomized controlled trials are required to validate the efficacy and safety of endovascular treatment in SDAVF patients.

Exotic domain-wall phenomena make ferroelectrics the candidates for nanoelectronics. The local symmetry and structure anomalies at domain walls have raised interest in the unusual functionalities, such as domain wall chirality and conductivity. Especially, the spontaneous lattice distortion and symmetry breaking at domain walls activate them as the location of structural transformation. However, the routes to achieve ferroelectric-antiferroelectric phase transition via ferroelectric domain walls remain challenging, which are important to develop materials for energy storage and conversion. Here, we have observed stepwise antiferroelectric phase transition in strained pure BiFeO3 ultrathin films derived from ferroelectric domain walls. Aberration-corrected transmission electron microscopy observation reveals that the resultant phase transition is mediated by dense 180° domain walls via providing the antiparallel cation displacement, cooperating with the enhanced interfacial oxygen octahedral clamping. First-principles calculations further confirm the critical role of interfacial oxygen octahedral coupling during this transition. These findings report an alternative route for antiferroelectric phase transition. Besides, our results provide fresh insights into functionalities of ferroelectric domain walls and open a venue for developing energy-storage materials based on domain engineering.

Retention failure is deleterious on ferroelectric domain stability, resulting in data loss in ferroelectric memories. However, the understanding of the origin of retention failure remains a challenge for the lack of a direct experimental evidence. Here, using a combination of piezoelectric force microscopy, atomic-scale scanning transmission electron microscopy and reciprocal space mapping, we report that the polarization retention failure is caused by a strain gradient induced flexoelectric field in tetragonal ferroelectric films. Atomic imaging reveals that the strain gradient is introduced by tensile strains, which is resultant from the vertically distributed Pb-rich anti-phase domains. This strain gradient couples with polarizations and results in flexoelectric fields in the films, leading to the retention failure in the films. Our study directly underlines the atomic mechanisms behind the strain gradient induced macroscopic retention failure behavior and clarifies the effect of local strain state on domain relaxation processes, thus can shed light on further understanding and improving the retention properties of oxide ferroelectrics.

Phase coexistence in ferroelectric oxide films displays complex phase competitions and transformation which suggest new multiple-coupled properties. Here we have successfully engineered the coexistence of flux-closure and a1/a2 phases in tensile-strained PbTiO3 films sandwiched between GdScO3 substrate and a SrTiO3 layer. Moreover, by using in-situ electron beam illumination, the unusual transformation from a1/a2 phase to the flux-closure phase was directly observed. In detail, there are two types of transformations: One is the nucleation, growth, and expansion of the flux-closure phase from the internal region of the a1/a2 phase. The other feature is a “dislocation gliding” like behavior: a thin lamella of a1/a2 shrinks like “partial dislocation pairs” and finally the gradually disappeared a1/a2 lamella forms a “perfect dislocation” in the flux-closure domain matrix. Phase-field simulations suggest that the a1/a2 to flux-closure transition is induced by the decrease of the depolarization field, which is screened by the injected electrons from electron beam irradiation. These results directly confirm the phase interconversion under an external stimulus at the nanometer scale, which shed new light on the fabrication of new polar textures.

Converse flexoelectricity is the mechanical strain induced by electric polarization gradients, which is largely omitted compared with the relatively well-known direct flexoelectricity. Thoroughly understanding the converse effect may not only explain peculiar structures generated by electric polarization or field gradients, but also stimulate new ideas to the design of novel electromechanical devices. In this work, the converse flexoelectricity around ferroelectric domain walls has been studied elaborately by synergetically integrating the aberration-corrected transmission electron microscope (TEM), first-principles calculations, and the Landau-Ginzburg-Devonshire (LGD) theory, taking prototypical tetragonal ferroelectric PbTiO3 as an example. We not only uncovered the important role of converse flexoelectricity on the asymmetric structure around 90° domain walls, but also quantified the flexoelectric coefficients. This quantification is deterministic in both the magnitude and sign of flexoelectric coefficients, by the mutual verification of the atomic mapping and first-principles calculations. Our results suggest that the converse flexoelectricity cannot be neglected for understanding ferroelectric DWs and other boundaries in ferroelectric materials.

A topological meron features a non-coplanar structure, whose order parameters in the core region are perpendicular to those near the perimeter. A meron is half of a skyrmion, and both have potential applications for information carrying and storage. Although merons and skyrmions in ferromagnetic materials can be readily obtained via inter-spin interactions, their behaviour and even existence in ferroelectric materials are still elusive. Here we observe using electron microscopy not only the atomic morphology of merons with a topological charge of 1/2, but also a periodic meron lattice in ultrathin PbTiO3 films under tensile epitaxial strain on a SmScO3 substrate. Phase-field simulations rationalize the formation of merons for which an epitaxial strain, as a single alterable parameter, plays a critical role in the coupling of lattice and charge. This study suggests that by engineering strain at the nanoscale it should be possible to fabricate topological polar textures, which in turn could facilitate the development of nanoscale ferroelectric devices. Merons are topological structures, but these have yet to be directly observed in ferroelectrics. Here, by epitaxially straining PbTiO3 on a SmScO3 substrate, electron microscopy and phase-field modelling allow the morphology and distribution of merons to be observed.

Ferroelectrics exhibit polarization tunable resistance switching behaviors, which are promising for next-generation non-volatile memory devices. For technological applications, thinner nanoscale arrays are expected, which feature with higher density and larger ON/OFF (RON/OFF) ratios in the metal/ferroelectrics/semiconductor heterojunction. Here, we acquire high density BiFeO3 (BFO) nano-islands around 10 nm in thickness displaying a high RON/OFF ratio of 103, comparable to the tunnel junctions. Moreover, both the macroscopic and microscopic resistive switching behaviors of the present BiFeO3 films reveal an unexpected the filamentary-type resistive switching which is modified by the charged domain walls in nano-islands dominated by the center-type domains. Particularly, the charged domain walls spontaneously formed within the BFO nano-islands are proposed as the conductive paths based on the redistribution of carriers under the applied voltages. Potential applications for memories with large RON/OFF ratios of such kind of configurable charged domain walls are demonstrated.

Manipulation of electronic states in functional ferroelectrics is promising for next generation electronics devices. The charged domain walls in ferroelectric materials especially facilitate the electronic state modulation and are promising for developing interface-based devices. However, the major challenges impeding the application are their intentional manipulation and the elusive pinning behavior. Here, results that charged domain walls in BiFeO3 films can be pinned and regulated by oxygen vacancy planar distributions controlled by oxygen pressure during film growth are reported. Using aberration-corrected scanning transmission electron microscopy complemented by theoretical simulations, rich pinning behavior of tail-to-tail charged domain walls by oxygen vacancy plates is revealed. At high annealing oxygen pressure, 71° charged domain walls are stabilized by narrow vacancy plates. Decreasing the oxygen pressure, the transformation from 71° to 109° charged domain walls happens by expanding the vacancy plates, as collaborated by phase field simulations. Besides, the 71°-109° charged domain wall pairs are stabilized due to further interaction between two neighboring vacancy plates. These results provide the active modulation of the electronic states and illuminate the rich pinning behavior of domain walls by vacancy defects in ferroelectrics, which in turn could provide implications for designing potential electronics devices.

The thermodynamic properties of impurity components in silicon solutions play an important role in the chemical removal process to the metallurgical route. In this paper, the component activity coefficients and interaction parameters of dilute silicon solutions were estimated by the molecular interaction volume model (MIVM). The activity coefficients (?i) of component i in dilute binary Si-i and ternary Si-i-j solutions at 1687-1873 K were firstly calculated. The concentration dependences of the interaction parameter and activity coefficient were also obtained. The self-interaction parameters (?i,i) for Si-i system were obtained as ?B,B= -2.728-362.031/T, ?Al,Al = 2.157-1876.776/T, ?Fe,Fe= -4.842+14445.926/T and ?P,P = -2.543+13767.036/T. At the same time, the interaction parameters among components B, Al, and Fe in dilute ternary Sii- j solutions were also derived as ?Fe,B=-1.2758-2946.306/T, ?Al,B = 0.7467-9765.9298/T and ?Fe,Al= -1.39677+3319.6803/T. Most important of all, the temperature dependences of the interaction parameters and activity coefficients in dilute Si-i and Si-i-j solutions with a certain i or j concentration were deduced. The results show that the predicted self-interaction parameters of B, Al, Fe, and P in binary silicon solutions reasonably agree with the experimental data. This further shows that MIVM is of reliability and can be expanded to a multi-component dilute silicon solution.

The cluster slave-spin method is implemented to research the ground state properties of the honeycomb lattice Hubbard model with doping $\delta$ and coupling $U$ being its parameters. At half-filling, a single direct and continuous phase transition between the semi-metal and antiferromagnetic (AFM) insulator is found at $U_{\text{AFM}}=2.43t$ that is in the Gross-Neveu-Yukawa universality class, where a relation between the staggered magnetization $M$ and the AFM energy gap $\Delta_{\text{AFM}}$ is established as $M \propto \Delta_{\text{AFM}}$, compared to $M \propto \Delta_{\text{AFM}} ( \ln{\Delta_{\text{AFM}}})^2$ in the square lattice case. A first-order semi-metal to the underlying paramagnetic (PM) insulator Mott transition is corroborated at $U_{\text{Mott}}=8.36t$, which is responsible for a broad crossover around $U_{c} = 5.4t$ between the weak- and strong-coupling regimes in the AFM state that increases with $\delta$, in contrast to the square lattice case. In the doped system, the compressibility $\kappa$ near the van Hove singularity at $\delta=1/4$ is suppressed substantially by the interaction before the semi-metal to AFM transition occurs, whereas $\kappa$ near the Dirac points is very close to the noninteracting one, indicating that the Dirac cone structure of the energy dispersion is rather robust. An overall phase diagram in the $U$-$\delta$ plane is presented, consisting of four regimes: the AFM insulator at $\delta=0$ for $U> U_{\text{AFM}}$, the AFM metal with compressibility $\kappa>0$ or $\kappa, Comment: 11 Figures and 12 Pages. The version that accepted for publication as a Regular Article in Physical Review B