Effect of external magnetic field on the instability of THz plasma waves in nanoscale graphene field-effect transistors

The instability of plasma waves in the channel of field-effect transistors will cause the electromagnetic waves with THz frequency.Based on a self-consistent quantum hydrodynamic model,the instability of THz plasmas waves in the channel of graphene field-effect transistors has been investigated with external magnetic field and quantum effects.We analyzed the influence of weak magnetic fields,quantum effects,device size,and temperature on the instability of plasma waves under asymmetric boundary conditions numerically.The results show that the magnetic fields,quantum effects,and the thickness of the dielectric layer between the gate and the channel can increase the radiation frequency.Additionally,we observed that increase in temperature leads to a decrease in both oscillation frequency and instability increment.The numerical results and accompanying images obtained from our simulations provide support for the above conclusions.

Effect of spin on the instability of THz plasma waves in field-effect transistors under non-ideal boundary conditions

Terahertz(THz) radiation can be generated due to the instability of THz plasma waves in field-effect transistors(FETs). In this work, we discuss the instability of THz plasma waves in the channel of FETs with spin and quantum effects under non-ideal boundary conditions. We obtain a linear dispersion relation by using the hydrodynamic equation, Maxwell equation and spin equation. The influence of source capacitance, drain capacitance, spin effects, quantum effects and channel width on the instability of THz plasma waves under the non-ideal boundary conditions is investigated in great detail. The results of numerical simulation show that the THz plasma wave is unstable when the drain capacitance is smaller than the source capacitance;the oscillation frequency with asymmetric boundary conditions is smaller than that under non-ideal boundary conditions;the instability gain of THz plasma waves becomes lower under non-ideal boundary conditions. This finding provides a new idea for finding efficient THz radiation sources and opens up a new mechanism for the development of THz technology.

基于超图的阿尔茨海默病辅助诊断研究现状与进展

阿尔茨海默病(Alzheimer's Disease,AD)等神经变性疾病普遍存在,记忆危机日益严重,因此对于早期AD辅助诊断的需求十分迫切。医学影像技术是前期辅助AD筛查的一种有效手段,其中超图在对AD分类任务中表现突出。在超图中,超边可以连接多个节点,这使得超图更适用于表示复杂的关系和结构。在医学影像技术中,超图能够更加准确地建模多元关系,具备较强的数据样本间非线性高阶关联的刻画和挖掘能力。汇总了基于脑功能超网络的研究成果,重点介绍了图核、矩阵分析、深度学习这3种方法,最后对未来的发展进行展望,为后续研究提供参考。

Protective Effects of Self-made Compound Taoren Danshen Decoction on Rats with Acute Liver Injury

[Objectives] To study the protective effects of self-made Compound Taoren Danshen Decoction( CTDD) on acute liver injury induced by D-galactosamine in rats,and to explore its mechanism. [Methods]An acute liver injury model was established by intraperitoneal injection of 500 mg/kg of D-galactosamine. The ALT,AST,MDA,SOD and GSH-Px in serum,as well as serum TNF-α,IL-1β and IL-6 levels were measured,and liver tissue lesions were observed under microscope. [Results] CTDD can significantly reduce ALT,AST and MDA levels,increase SOD,GSH-Px activity,and significantly reduce serum TNF-α,IL-1β and IL-6 levels,and improve liver tissue lesions.[Conclusions]CTDD has a protective effect on D-galactosamine-induced acute liver injury in rats,and its mechanism may be related to inhibition of oxidative stress and inflammatory reaction.

Rh-Cu alloy nano-dendrites with enhanced electrocatalytic ethanol oxidation activity

The application of direct ethanol fuel cell(DEFC)has been bottlenecked by the sluggish ethanol oxidation reaction(EOR).Efficient electrocatalysts for the C-C bond cleavage are essential to promote EOR with high efficiency and C1 selectivity.Here,we prepared Rh-Cu alloy nano-dendrites(RhCu NDs)with abundant surface steps through controlled co-reduction,which exhibited significantly enhanced activity and C1 selectivity(0.47 m A cm_((ECSA))^(-2),472.4 mA mg_(Rh)^(-1),and 38.9%)than Rh NDs(0.32 mA cm((ECSA))-2,322.1 mA mgRh-1,and 21.4%)and commercially available Rh/C(0.18 mA cm_((ECSA))^(-2),265.4 mA mg_(Rh)^(-1),and 14.9%).Theoretical calculations and CO-stripping experiments revealed that alloying with Cu could modulate the surface electronic structures of Rh to resist CO-poisoning while strengthening ethanol adsorption.In situ Fourier transform infrared spectroscopy(FTIR)indicated that the surface steps on RhCu NDs further promoted the C-C bond cleavage to increase the C1 selectivity.Therefore,optimizing the surface geometric and electronic structures of nanocrystals by rational composition and morphology control can provide a promising strategy for developing practical DEFC devices.

检出限与灵敏度关系及影响因素的探讨

检出限和灵敏度是评价分析方法的两个重要指标。国际纯粹与应用化学联合会(IUPAC)等对检出限和灵敏度的定义给出了明确的推荐。但是,有些教材和学术论文中检出限和灵敏度的使用仍然较为混乱。本文归纳了检出限和灵敏度的定义和计算方法,讨论了现代分析方法检出限和灵敏度的影响因素,提出了降低检出限和提高灵敏度的一些策略。

Comparison of Laparotomy and Laparoscopic Surgery for Ectopic Pregnancy at High Altitude

In this paper,by comparing the clinical effects of laparotomy and laparoscopy on the recovery of ectopic pregnancy,70 patients with ectopic pregnancy in the people's Hospital of Tibet Autonomous region from April 2017 to April 2019 were selected as the control group who received laparotomy.35 patients in each group were treated by laparoscopy to compare the recovery of the two groups.To solve the problem of which method of operation for ectopic pregnancy in plateau area is better,and to promote the operation for better recovery of patients in the future.

Solid rocket motor propellant grain burnback simulation based on fast minimum distance function calculation and improved marching tetrahedron method

To efficiently compute arbitrary propellant grain evolution of the burning surface with uniform and non-uniform burning rate for solid rocket motor,a unified framework of burning surface regression simulation has been developed based on minimum distance function.In order to speed up the computation of the mini-mum distance between grid nodes of grain and the triangular mesh of burning surface,a fast distance querying method based on the equal size cube voxel structure was employed.An improved marching tetrahedron method based on piecewise linear approximation was carried out on second-order tetrahedral elements,achieved high-efficiency and adequate accuracy of burning surface extraction simultaneously.The cases of star grain,finocyl grain,and non-uniform tube grain were studied to verify the proposed method.The observed result indicates that the grain burnback computation method could realize the accurate simulation on unstructured tetrahedral mesh with a desirable performance on computational time.

VEGF-B prevents excessive angiogenesis by inhibiting FGF2/FGFR1 pathway

Although VEGF-B was discovered as a VEGF-A homolog a long time ago,the angiogenic effect of VEGF-B remains poorly understood with limited and diverse findings from different groups.Notwithstanding,drugs that inhibit VEGF-B together with other VEGF family members are being used to treat patients with various neovascular diseases.It is therefore critical to have a better understanding of the angiogenic effect of VEGF-B and the underlying mechanisms.Using comprehensive in vitro and in vivo methods and models,we reveal here for the first time an unexpected and surprising function of VEGF-B as an endogenous inhibitor of angiogenesis by inhibiting the FGF2/FGFR1 pathway when the latter is abundantly expressed.Mechanistically,we unveil that VEGF-B binds to FGFR1,induces FGFR1/VEGFR1 complex formation,and suppresses FGF2-induced Erk activation,and inhibits FGF2-driven angiogenesis and tumor growth.Our work uncovers a previously unrecognized novel function of VEGF-B in tethering the FGF2/FGFR1 pathway.Given the anti-angiogenic nature of VEGF-B under conditions of high FGF2/FGFR1 levels,caution is warranted when modulating VEGF-B activity to treat neovascular diseases.

基于互样本熵脑网络的脊髓电刺激下微意识状态患者脑功能评估

脊髓电刺激作为一种有效的意识促醒手段已经在临床上得到了较为广泛的应用,但是其内在机制仍不完全明确.本文将正常人静息态脑电作为对照组,利用样本熵对微意识状态患者的脊髓电刺激前后的脑电信号进行计算,并分析了基于互样本熵构造的脑网络在刺激前后的变化.结果表明,脊髓电刺激提高了微意识状态患者额叶和中央区内的脑电信号复杂度;还提高了患者在额叶内、中央区内以及额叶与其他脑区间的高频段(α~γ,8~45 Hz)的耦合模式复杂度,表明通道间信息交互作用的显著增强;同时,患者高频段脑网络平均聚类系数增加,平均特征路径长度减少,小世界特性显著提升(在α,β,和γ均为p<0.001).相对于健康对照组,这些指标变化的方向趋向于正常人静息态的脑功能.样本熵和互样本熵在脊髓电刺激后与健康对照组在某些脑区内或脑区间上无显著差异(比如,β和γ频段的样本熵值在额叶和中央区(p>0.05)),但是高频段的脑网络参数仍有显著差异(比如,高频段小世界网络特征p<0.001).因此,我们认为这些变化是脊髓电刺激对大脑产生了一个"短时程效应".我们推测脊髓电刺激对脑功能的重塑有一定的促进作用.本研究对脊髓电刺激的内在机理提供了新的解释,同时也为微意识状态患者的脑功能评估提供了新的思路.

Energy dissipation mechanism and experiment of particle dampers for gear transmission under centrifugal loads

As a passive means of vibration reduction, particle damping is mainly applied to the horizontal or vertical steady field. However, it is seldom applied to centrifugal fields. Under high speed and heavy loading, the vibration of tooth surfaces of gear transmissions becomes more severe shortening gear service life and augmenting noise. Under centrifugal loading, the particle system exhibits different characteristics, for example, particles are extruded at the end farthest from the center. We investigated gears with drilled via holes filled with damping particles. Using the discrete-element method, we developed an energy dissipation model for the particle system accounting for friction and inelastic collisions. Energy dissipation and damping characteristics of this system were analyzed. Experiments were also conducted with the gear system having different particle filling rates. The results show that this filling rate is an important parameter associated with particle damping in a centrifugal field. An unsuitable filling rate would significantly reduce damping effectiveness. With changes in rotation speed and load, the gear transmission system has different optimal filling rates. The results provide guidelines for the application of particle damping in centrifugal fields of gear transmissions.

Multi-twinned gold nanoparticles with tensile surface steps for efficient electrocatalytic CO_(2) reduction

CO_(2) reduction reactions(CO_(2)RR) powered by renewable electricity can directly convert CO_(2) to hydrocarbons and fix the intermittent sustainable energy in portable chemical fuels. It is of great importance to develop advanced catalysts that can boost CO_(2)RR with high activity, selectivity, and efficiency at low overpotentials. Here, we report the solution synthesis using H_(2)O_(2) to modify the surface structures of gold multi-twinned nanoparticles(AuMPs) and create tensile surface steps. Calculations predicted significantly enhanced CO_(2) adsorption and boosted CO_(2)RR capabilities with inhibited hydrogen evolution reaction activity for the tensile surface steps with modified electronic structure. The H_(2)O_(2)-treated AuMPs with surface steps and 3.83% tensile lattices showed much higher activity and selectivity at lower overpotentials for CO_(2)RR than pristine gold nanoparticles.The CO-production current density reached about 98 mA cm^(-2) with a Faradaic efficiency of 95.7% at -0.30 V versus reversible hydrogen electrode in the flow cell, showing a half-cell energy efficiency as high as ~83%. Our strategy represents a rational catalyst design by engineering the surface structures of metal nanoparticles and may find more applicability in future electrocatalysis.