Potential Value of Wood Tar as a Natural Fungicide against Valsa mali

The Valsa canker caused by Valsa mali seriously harmed the production of East Asian apples and caused very significant economic losses. Considering the chemical residues and the improvement of people’s awareness of environmental protection, there is a need for screening new green pesticides for the control of Valsa canker. Therefore, we conducted systematic evaluations on the antifungal activity of wood tar. In this research, the effective concentration (EC₅₀) of six strains of V. mali to wood tar was determined, and the EC₅₀ ranged from 69.54 to 92.81 μg/mL. After treatment with wood tar, the hyphae of V. mali broke, swelled, and deformed; the permeability of the cell membrane increased; and the activity of pectinase reduced. Moreover, the expression levels of five genes related to pectinase also decreased significantly. In addition, the activities of phenylalanine ammonia lyase (PAL) and peroxidase (POD) of apple leaves treated with wood tar also increased. On detached apple branches, wood tar also showed therapeutic and protective activities. In the 2016–2019 field experiments, wood tar also showed good efficacy against Valsa canker and promoted the formation of callus. (In the experiments from 2016 to 2019, it can be seen that the control effect of 50% wood tar and 100% wood tar in the field is above 75% and promoted the formation of callus.) This study is the first to report the bidirectional efficacy of wood tar against Valsa mali and for trunk wound healing. The above results evidenced that wood tar has great potential to be developed as a natural alternative to commercial fungicides for the management of apple Valsa canker.     

2.45GHz ECR 强流等离子体源核心部件设计与实验研究

电子回旋共振(Electron Cyclotron Resonance,ECR)等离子体源能产生高电荷态离子、高流强的单电荷态离子,提供稳定的束流和良好的重复性.核心部件的设计对ECR等离子体源是至关重要的,磁场对等离子体的生成和分布有直接影响,良好的磁场可以提高等离子体的性能和效率.采用有限元分析方法对ECR等离子体源磁场进行分析与设计,得到了满足设计需求与目标的磁场位形,通过高斯计对设计的永磁环轴向磁场精确测量,发现磁场仿真结果与实验结果吻合比较好,只是轴向磁场最大值及对应位置上有点偏差.通过集成实验,研究核心部件对离子源引出束流强度的影响,引出束流稳定且强度达到7 m A.     

共轭高聚物双分子结构中激子电致解离的动力学研究

通过绝热动力学方法,研究了共轭高聚物双分子结构中激子对外加电场的响应.当外电场强度超过某个临界值时,激子会被解离成一对自由的电子与空穴.对于双分子结构中的激子,其临界解离电场除了受电子与电子相互作用以及电声相互作用影响之外,还受分子间相互作用的影响.由动力学演化的计算得到,激子临界解离电场强度随分子间相互作用强度的增大而呈非线性降低;随电子与电子相互作用强度的增大呈非线性减小的变化;但是,随电声耦合强度的增大却呈现出线性增大的变化.     

荷电颗粒在旋转环形通道内分离性能研究

为研究带电旋转环形通道内荷电颗粒的运动和沉积特性,本文使用计算流体力学两相流离散颗粒法对带电旋转环形通道内的荷电颗粒的运动过程进行了模拟。根据模拟结果分析了不同粒径、电压、入口雷诺数和通道长径比等参数对荷电颗粒运动和沉积的影响,研究了荷电颗粒在旋转通道内离心力与电场力之间的竞争关系,探索了离心力和电场力导致的荷电颗粒运动和沉积变化的规律。结果表明,单个不同粒径颗粒具有不同的颗粒逃逸电压区间,区间的大小随着颗粒粒径的增大而增大,且区间的宽度随着通道长径比的增大将会明显变小;多个颗粒的逃逸率曲线,不同粒径的颗粒将会有不同程度的交叉,随着长径比的增大,颗粒逃逸率曲线的高度与交叉会有明显的减小,而随着转速的增大,颗粒逃逸率曲线的交叉会有一定程度的减小,且高度不会有明显变化。     

基于概率密度演化的输电塔-线体系抗风可靠性分析

以三线两塔直线段输电塔-线体系为工程对象,应用有限元数值模拟,建立了基于概率密度演化的输电塔-线体系抗风可靠性分析方法。首先,应用谱表示-降维方法模拟结构脉动风场,生成风荷载的代表性样本集合。然后,结合概率密度演化理论,分析了输电塔-线体系考虑气弹效应的随机动力反应。最后,应用等价极值思想构建了风荷载作用下输电塔-线体系失效准则,进而对输电塔-线体系的抗风可靠性进行精细化分析。本文结合谱表示-降维方法与概率密度演化理论,实现了仅用较少数量的代表性样本来精细地分析结构的抗风可靠性,为工程实践提供参考。     

Cooperative emission study in ytterbium doped NdVO4

The infrared and visible cooperative emissions of ytterbium ions are studied in Yb-doped NdVO₄ single crystals. The absorption of optical phonons allows the emissions at room temperature when a Nd:YAG laser is used. Low temperature emissions are observed due to the Nd³⁺→Yb³⁺ energy transfer following an argon ion laser excitation of the Nd³⁺ ions. Analysis of the cooperative emission at low doping concentration (1%) indicates that it is generated by distant pair forming Yb³⁺ ions while at high doping concentration (≥ 5%) close ions magnetically coupled and superexchange mechanisms prevail in the emitting process.     

Magnetic moment of phonons in graphene induced by a magnetic field

A magnetic field not only changes the electronic structure in graphene but also affects the phonon excitations via the electron-phonon interaction and even enables the phonons to generate magnetism. In this paper, we evaluate the magnetic moment of phonons in graphene using a generating-functional technique. The calculation results indicate that the phonon magnetic moment exists only in a weak magnetic field. The step-like change of the magnetic moment with the magnetic field reflects a macroscopic quantum effect.     

Electron paramagnetic resonance imaging using magnetic-field-gradient spinning

A novel X-band CW EPR imaging has been developed using magnetic-field-gradient (MFG) spinning to obtain spatial distributions of electron paramagnetic species. Spinning MFG EPR imaging for 65 projection spectra required just 55 s while conventional imaging took 11 min 40 s, that is, the acquisition time for the new system is one order of magnitude shorter than that for conventional EPR imaging. Spinning MFG EPR imaging allows one to measure reconstructed images in an interactive manner where resolution and condition can be changed quickly.     

HM-J16双光子电子直线加速器

简要叙述了HM-J16加速器的设计思想和设计特点。设计了一台采用射频功率反馈的射线能量范围为6～16MeV的双光子电子直线加速器。其最大辐射野为40cm×40cm,双光子剂量率均大于360cGy/(min×m)。     

提高单层GeSe对H2O气体传感性能的第一性原理研究

采用第一性原理计算方法,通过在单层GeSe上施加双轴向应变、外加电场、掺Ag等途径来探索提高单层GeSe对H₂O分子传感性能的有效方法,并从微观角度阐明内在机理.计算结果表明,-1.0 V/?的外加电场能有效降低H₂O分子在单层GeSe的吸附能并使二者之间的电荷转移量增加11倍,显著提高了单层GeSe对H₂O分子的响应速度和敏感性.研究结果为进一步设计并制成二维GeSe基湿度传感器提供了理论依据.