Linear magnetoconductivity in an intrinsic topological Weyl semimetal

Searching for the signature of the violation of chiral charge conservation in solids has inspired a growing passion on the magneto-transport in topological semimetals. One of the open questions is how the conductivity depends on magnetic fields in a semimetal phase when the Fermi energy crosses the Weyl nodes. Here, we study both the longitudinal and transverse magnetoconductivity of a topological Weyl semimetal near the Weyl nodes with the help of a two-node model that includes all the topological semimetal properties. In the semimetal phase, the Fermi energy crosses only the 0th Landau bands in magnetic fields. For a finite potential range of impurities, it is found that both the longitudinal and transverse magnetoconductivity are positive and linear at the Weyl nodes, leading to an anisotropic and negative magnetoresistivity. The longitudinal magnetoconductivity depends on the potential range of impurities. The longitudinal conductivity remains finite at zero field, even though the density of states vanishes at the Weyl nodes. This work establishes a relation between the linear magnetoconductivity and the intrinsic topological Weyl semimetal phase.Comment: An extended version accepted by New. J. Phys. with 15 pages and 3 figure

High-field magnetoconductivity of topological semimetals with short-range potential

Weyl semimetals are three-dimensional topological states of matter, in a sense that they host paired monopoles and antimonopoles of Berry curvature in momentum space, leading to the chiral anomaly. The chiral anomaly has long been believed to give a positive magnetoconductivity or negative magnetoresistivity in strong and parallel fields. However, several recent experiments on both Weyl and Dirac topological semimetals show a negative magnetoconductivity in high fields. Here, we study the magnetoconductivity of Weyl and Dirac semimetals in the presence of short-range scattering potentials. In a strong magnetic field applied along the direction that connects two Weyl nodes, we find that the conductivity along the field direction is determined by the Fermi velocity, instead of by the Landau degeneracy. We identify three scenarios in which the high-field magnetoconductivity is negative. Our findings show that the high-field positive magnetoconductivity may not be a compelling signature of the chiral anomaly and will be helpful for interpreting the inconsistency in the recent experiments and earlier theories.Comment: An extended version accepted by Phys. Rev. B, with 11 pages and 4 figure

Edge states and integer quantum Hall effect in topological insulator thin films

The integer quantum Hall effect is a topological state of quantum matter in two dimensions, and has recently been observed in three-dimensional topological insulator thin films. Here we study the Landau levels and edge states of surface Dirac fermions in topological insulators under strong magnetic field. We examine the formation of the quantum plateaux of the Hall conductance and find two different patterns, in one pattern the filling number covers all integers while only odd integers in the other. We focus on the quantum plateau closest to zero energy and demonstrate the breakdown of the quantum spin Hall effect resulting from structure inversion asymmetry. The phase diagrams of the quantum Hall states are presented as functions of magnetic field, gate voltage and chemical potential. This work establishes an intuitive picture of the edge states to understand the integer quantum Hall effect for Dirac electrons in topological insulator thin films.Comment: 10 pages, 5 figure

High frequency switching parallel processing topology for AC uninterruptible power supply

This thesis presents the description, analysis and design of a high frequency parallel processing ac uninterruptible power supply. Compared to the standard UPS system used today, the proposed system has higher efficiency, smaller size and less weight, this is due primary to the usage of a high-frequency switching topology. The main power circuit configuration is shown to describe the steady state behaviour of the system in both ac line supply and battery backup modes of operation. A stability analysis is developed to describe the system behaviour against the load variation and the input disturbance. The detailed design of the output voltage control loop is carried out. A transient analysis is presented to describe the transition between the two operation modes of ac line supply and dc battery backup. From this analysis a fast switching transition control circuit is designed. A design procedure is illustrated to select the system components for a 300W UPS. The corresponding system performance such as efficiency is evaluated. All the theoretical results obtained in this thesis are experimentally verified

A New Method for Figuring the Number of Hidden Layer Nodes in BP Algorithm

In the field of artificial neural network, BP neural network is a multi-layer feed-forward neural network. Because it is difficult to figure the number of hidden layer nodes in a BP neural network, the theoretical basis and the existing methods for BP network hidden layer nodes are studied. Then based on traditional empirical formulas, we propose a new approach to rapidly figure the quantity of hidden layer nodes in two-layer network. That is, with the assistance of experience formulas, the horizon of unit number in hidden layer can be confirmed and its optimal value will be found in this horizon. Finally, a new formula for figuring the quantity of hidden layer codes is obtained through fitting input dimension, output dimension and the optimal value of hidden layer codes. Under some given input dimension and output dimension, efficiency and precision of BP algorithm may be improved by applying the proposed formula

PO-161 Effect of different type of exercise on mitochondrial homeostasis in rats with myocardial infarction

Objective To investigate the different effect of moderate-intensity continuous training (MCT) and high-intensity interval exercise training (HIT) on ventricular remodeling and mitochondrial homeostasis after acute myocardial infarction (AMI). Methods The AMI rat model was achieved by ligating coronary artery. The AMI and sham operation rats were randomly divided into four groups: sham operation group (Sham), AMI control group (AMI), AMI MCT group (AMI+M), and AMI HIT group (AMI+H). Animals in the AMI+M and AMI+H groups underwent 4 weeks MCT and HIT respectively. Five weeks after AMI, hemodynamic changes, mitochondrial bioenergetics, and PINK1, Beclin1, Mfn2, Drp1, Tfam, COXⅣ, PGC-1α were detected. Results Comparing with AMI group, in AMI+M and AMI+H groups, Beclin1 (146.33±18.47, 143.28±16.96.vs. 123.27±13.27, P<0.05), PINK1 (150.33±20.54, 152.28±18.34.vs. 125.27±17.67, P<0.05), Mfn2 (122.28±18.81, 117.19±17.04.vs. 46.27±6.72, P<0.01), and PGC-1α (82.15±16.58, 102.25±13.27.vs. 60.27±9.36, P<0.05~0.01) expression elevated significantly, whereas ROS generation (122.28±18.81, 117.19±17.04.vs. 46.27±6.72, P<0.01) and Drp1 expression (9.58±1.40, 10.18±1.37.vs. 15.85±1.61, P<0.05) showed dramatic decrease. In addition, in AMI+H group, +dp/dt max (6326±325.vs. 5368±271, P<0.05), -dp/dt max (-5312±246.vs. -4457±250, P<0.05), mitochondrial membrane potential (85.24±11.94.vs. 71.28±8.34, P<0.05), ATP synthesis activity (38.77±5.16.vs. 32.33±4.14, P<0.05), Tfam (95.25±12.05.vs. 78.27±12.22, P<0.05) and COXⅣ (89.25±14.06.vs. 67.27±13.71, P<0.05) expression improved significantly. Comparing with AMI+M group, in AMI+H group, +dp/dt max (6326±325.vs. 5775±310, P<0.05), -dp/dt max (-5312±246.vs. -4778±305, P<0.05), PGC-1α (102.25±13.27.vs. 82.15±16.58 1, P<0.05), Tfam (95.25±12.05.vs. 80.15±11.99, P<0.05) and COXⅣ(89.25±14.06.vs. 72.15±10.89, P<0.05) expression improved significantly. Conclusions High-intensity interval exercise training is superior to moderate-intensity continuous training for ameliorating ventricular remodeling and mitochondrial homeostasis after acute myocardial infarction

非甾体抗炎药相关的消化性溃疡并发上消化道出血

Through discussion of 1 elderly case with multiple drug application of upper gastrointestinal bleeding (UGIB), we have summarized non-steroidal anti-inflammatory drugs (NSAIDs) are responsible for peptic ulcer bleeding, then discussed the relationship between drugs and peptic ulcer bleeding, suggested current researches of the factors such as age and Helicobacter pylori infection are bleeding risk to recurrent peptic ulcer complicated with UGIB. At last, we suggested the specifec therapeutic schedule and treat focus in different periods.通过讨论1例有应用多种药物病史的老年上消化道出血病例，分析了导致该患者发生消化性溃疡进而发生上消化道出血的致病因素主要与非甾体类消炎药密切相关，同时讨论了多种药物在致病中的主要作用与促发作用。该患者年龄大，既往有胃溃疡病史，同时有幽门螺杆菌感染则是易于再发消化性溃疡并发上消化道出血的易发因素。根据上述分析提出了具体的治疗方案以及不同时期的治疗重点