A sample-position-autocorrection system with precision better than 1 \um~in angle-resolved photoemission experiments

We present the development of a high-precision sample-position-autocorrection system for photoemission experiments. A binocular vision method based on image pattern matching calculations was realized to track the sample position with an accuracy better than 1 \um, which was much smaller than the spot size of the incident laser. We illustrate the performance of the sample-position-autocorrection system with representative photoemission data on the topological insulator Bi$_2$Se$_3$ and an optimally-doped cuprate superconductor \Bi. Our method provides new possibilities for studying the temperature-dependent electronic structures in quantum materials by laser-based or spatially resolved photoemission systems with high precision and efficiency.Comment: 6 pages, 4 figure

Ultrafast Switching from the Charge Density Wave Phase to a Metastable Metallic State in 1T-TiSe2_2

The ultrafast electronic structures of the charge density wave material 1T-TiSe$_2$ were investigated by high-resolution time- and angle-resolved photoemission spectroscopy. We found that the quasiparticle populations drove ultrafast electronic phase transitions in 1T-TiSe$_2$ within 100 fs after photoexcitation, and a metastable metallic state, which was significantly different from the equilibrium normal phase, was evidenced far below the charge density wave transition temperature. Detailed time- and pump-fluence-dependent experiments revealed that the photoinduced metastable metallic state was a result of the halted motion of the atoms through the coherent electron-phonon coupling process, and the lifetime of this state was prolonged to picoseconds with the highest pump fluence used in this study. Ultrafast electronic dynamics were well captured by the time-dependent Ginzburg-Landau model. Our work demonstrates a mechanism for realizing novel electronic states by photoinducing coherent motion of atoms in the lattice.Comment: 13 Pages, 10 figure

BnMs3 is required for tapetal differentiation and degradation, microspore separation, and pollen-wall biosynthesis in Brassica napus

7365AB, a recessive genetic male sterility system, is controlled by BnMs3 in Brassica napus, which encodes a Tic40 protein required for tapetum development. However, the role of BnMs3 in rapeseed anther development is still largely unclear. In this research, cytological analysis revealed that anther development of a Bnms3 mutant has defects in the transition of the tapetum to the secretory type, callose degradation, and pollen-wall formation. A total of 76 down-regulated unigenes in the Bnms3 mutant, several of which are associated with tapetum development, callose degeneration, and pollen development, were isolated by suppression subtractive hybridization combined with a macroarray analysis. Reverse genetics was applied by means of Arabidopsis insertional mutant lines to characterize the function of these unigenes and revealed that MSR02 is only required for transport of sporopollenin precursors through the plasma membrane of the tapetum. The real-time PCR data have further verified that BnMs3 plays a primary role in tapetal differentiation by affecting the expression of a few key transcription factors, participates in tapetal degradation by modulating the expression of cysteine protease genes, and influences microspore separation by manipulating the expression of BnA6 and BnMSR66 related to callose degradation and of BnQRT1 and BnQRT3 required for the primary cell-wall degradation of the pollen mother cell. Moreover, BnMs3 takes part in pollen-wall formation by affecting the expression of a series of genes involved in biosynthesis and transport of sporopollenin precursors. All of the above results suggest that BnMs3 participates in tapetum development, microspore release, and pollen-wall formation in B. napus

An NUTSF at Sub-Region for Suppression of Torque Ripple in Switched Reluctance Motors

The conventional torque sharing function (TSF) control strategy in a switched reluctance motor (SRM) has higher torque ripple due to the weak torque tracking ability with an increase in speed. A non-unity torque sharing function (NUTSF) is proposed in order to minimize the torque ripple. Firstly, the working principle of the conventional TSF is introduced, and the causes of higher torque ripple are analyzed. Secondly, the NUTSF control strategy at each sub-region, where the two-phase exchange region is further divided into region 1 and region 2 based on the inductance characteristics, is proposed, and an optimization algorithm at each sub-region is applied so that the TSF is more suitable for the inductance and torque characteristics of the motor. Finally, a three-phase 6/20 SRM is taken as an example for simulation analysis and a prototype experiment. The results show that the proposed control strategy can effectively reduce the torque ripple of an SRM at a wide speed range

An NUTSF at Sub-Region for Suppression of Torque Ripple in Switched Reluctance Motors

The conventional torque sharing function (TSF) control strategy in a switched reluctance motor (SRM) has higher torque ripple due to the weak torque tracking ability with an increase in speed. A non-unity torque sharing function (NUTSF) is proposed in order to minimize the torque ripple. Firstly, the working principle of the conventional TSF is introduced, and the causes of higher torque ripple are analyzed. Secondly, the NUTSF control strategy at each sub-region, where the two-phase exchange region is further divided into region 1 and region 2 based on the inductance characteristics, is proposed, and an optimization algorithm at each sub-region is applied so that the TSF is more suitable for the inductance and torque characteristics of the motor. Finally, a three-phase 6/20 SRM is taken as an example for simulation analysis and a prototype experiment. The results show that the proposed control strategy can effectively reduce the torque ripple of an SRM at a wide speed range

An Analytic Method of Segmented PWM Duty Cycle for Switched Reluctance Motor

In view of the large current peak and torque ripple in the actual current chopping control of switched reluctance motor, a segmented PWM duty cycle analysis method of switched reluctance motor based on current chopping control is proposed in this paper. The method realizes the control of the winding current by adjusting the average voltage of the two ends of the winding in one cycle through the PWM duty cycle. At the same time, according to the inductance linear model, the conduction phase is divided into a small inductance region and an inductance rising region, and the analytical formulas of PWM duty cycle in the two regions are deduced respectively. Finally, through matlab/simulink simulation and motor platform experiment, the current chopping control is compared with the segmented PWM duty cycle analysis method in this paper. Simulation and experimental results show that the segmented PWM duty cycle analysis method can effectively reduce the current peak and torque ripple, and has high practical application value

Design and optimization of reverse salient permanent magnet synchronous motor based on controllable leakage flux

In this paper, a controllable leakage flux reverse salient permanent magnet synchronous motor (CLF-RSPMSM) is designed, which has the advantages of wide speed range and low irreversible demagnetization risk. Firstly, the principle of controllable leakage flux and reverse saliency effect is introduced, and the design of the rotor flux barrier is emphatically discussed. Secondly, multiple design variables are stratified by the comprehensive sensitivity method, and the main variables are screened out. Then the relationship between the main variables and the optimization goal is discussed according to the response surface diagram. Thirdly, a sequential nonlinear programming algorithm (SNP) is used to optimize the three optimization objectives comprehensively. Finally, the electromagnetic performance of the proposed motor is compared with the initial IPM motor, the mechanical strength of the proposed rotor is analyzed, and the results verify the effectiveness of the design and optimization method of the proposed motor

Anomalous contribution to the nematic electronic states from the structural transition in FeSe revealed by time- and angle-resolved photoemission spectroscopy

High-resolution time- and angle-resolved photoemission measurements were made on FeSe superconductors. With ultrafast photoexcitation, two critical excitation fluences that correspond to two ultrafast electronic phase transitions were found only in the $d_{yz}$-orbit-derived band near the Brillouin-zone center within our time and energy resolution. Upon comparison to the detailed temperature dependent measurements, we conclude that there are two equilibrium electronic phase transitions (at approximately 90 and 120 K) above the superconducting transition temperature, and an anomalous contribution on the scale of 10 meV to the nematic states from the structural transition is experimentally determined. Our observations strongly suggest that the electronic phase transition at 120 K must be taken into account in the energy band development of FeSe, and, furthermore, the contribution of the structural transition plays an important role in the nematic phase of iron-based high-temperature superconductors.Comment: 9 pages, 5 figure

(−)-Epigallocatechin gallate alleviates chronic unpredictable mild stress-induced depressive symptoms in mice by regulating the mTOR autophagy pathway and inhibiting NLRP3 inflammasome activation

Depression is a global public health issue that is widely studied due to the large number of people it affects and its serious consequences. Clinical studies have shown that regular tea consumption may reduce depression risk. (−)-Epigallocatechin gallate (EGCG), the main tea polyphenol, was observed to alleviate depression, but the underlying mechanism has not been elucidated. In this study, chronic unpredictable mild stress (CUMS) was used to induce depression-like behavior in mice, and behavioral tests, such as sucrose preference test and forced swim test, were performed. Then, ELISA, western blot and QT-PCR tests were used to assess the expression of the key components of the NLRP3 inflammasome and its downstream inflammatory effectors (e.g., IL-1β, IL-18), autophagy markers (Beclin-1, LC3, P62) and apoptosis markers (Bax, Bcl-2) in mouse brain tissues. Changes in serum lipid levels were also assessed. EGCG alleviated CUMS-induced depression-like behavioral changes in mice, reduced activation of the NLRP3 inflammasome, inhibited the mTOR signaling pathway, restored autophagy levels, reduced apoptosis marker expression and attenuated abnormal changes in blood lipid levels. Our study demonstrates that EGCG exerts antidepressive effects through multiple mechanisms, providing new insight into the pathological mechanism of depression and laying the foundation for the development of new therapeutic measures