Effects of Spatial Variation of Thermal Electrons on Whistler-Mode Waves in Magnetosphere

A ray-tracing method is developed to evaluate the wave growth/damping and specifically propagation trajectories of the magnetospherically reflected Whistler-mode waves. The methodology is valid for weak wave growth/damping when plasma is comprised of a cold electron population and a hot electron population, together with background neutralizing ions, e.g. protons. The effect of anisotropic thermal electrons on the propagation of Whistler-mode waves is studied in detail. Numerical results are obtained for a realistic spatial variation model of plasma population, including the cold electron density distribution, and the thermal electron density and temperature distribution. It is found that, analogous to the case of the typical cold plasma approximation, the overall ray path of Whistler-mode waves is insensitive to the thermal electron density and temperature anisotropy, and the ray path reflects where wave frequency is below or comparable to the local lower hybrid resonance frequency flhr. However, the wave growth is expected to be influenced by the thermal electron population. The results present a first detailed verification for the validity of the typical cold plasma approximation for the propagation of Whistler-mode waves and may account for the observation that the Whistler-mode waves tend to propagate on a particular magnetic shell L where the wave frequency is comparable to fthe.     

Energetic Electron Pitch Angle Diffusion due to Whistler Wave during Terrestrial Storms

A concise and elegant expression of cyclotron harmonic resonant quasi-pure pitch-angle diffusion is constructed for the parallel whistler mode waves, and the quasi-linear diffusion coefficient is prescribed in terms of the whistler mode wave spectral intensity. Numerical computations are performed for the specific case of energetic electrons interacting with a band of frequency of whistler mode turbulence at L ≈ 3. It is found that the quasi-pure pitch-angle diffusion driven by the whistler mode scatters energetic electrons from the larger pitch-angles into the loss cone, and causes pitch-angle distribution to evolve from the pancake-shaped before the terrestrial storms to the flat-top during the main phase. This probably accounts for the quasi-isotropic pitch-angle distribution observed by the combined release and radiation effects satellite spacecraft at L ≈ 3.     

Synthesis and Crystal Structure of 4-Arylamino-6-chloropyrido[3,2-d]pyrimidine

The title compounds 4a～c were synthesized and characterized by IR,NMR and MS.The crystal structure of C16H13ClN4O2·HBr·H2O(I),the quaternary ammonium salt of 4c,was determined by X-ray diffraction analysis.I crystallizes in triclinic,space group P1 with a = 8.3121(8),b = 9.3885(8),c = 13.2903(12),α = 106.788(2),β = 95.204(3),γ = 110.871(2)o,V = 905.81(14)3,Z = 2,C16H16BrClN4O3,Mr = 427.68,Dc = 1.568 g/cm3,F(000) = 432.00,μ = 2.446 mm-1,R = 0.0496 and wR = 0.127.X-ray analysis reveals that C(15) in the BrCH2COOH molecule binds to the N(1) of pyrimidine ring to form the quaternary ammonium salt.Two adjacent I molecules are connected by hydrogen bonds through carboxylate oxygen,water molecule and hydrobromic acid.     

MgO高温高压特性及相变的第一性原理研究

应用第一性原理密度泛函理论计算了MgO在零温(0K)下和0~200GPa静水压范围内的晶体结构和弹性模量,以及B1、B4和B8相结构的MgO的声速随压力的变化。利用准简谐近似下的Debye模型,通过拟合三阶Birch-Murnaghan物态方程模拟了高温效应并对三个相在高温高压下的相稳定性做了研究。本工作的计算结果与前人的理论和实验结果符合较好,说明第一性原理结合准简谐Debye模型能够比较准确的模拟矿物如MgO在高温高压下的热力学性质。     

Modelling Energetic Electrons by a Kappa-Loss-Cone Distribution at Geostationary Orbit

We adopt a recently developed relativistic kappa-loss-cone （KLC） distribution to model energetic electrons energy spectra observed at the geostatlonary orbit in the storm of 3-4 November 1993. The KLU distribution is found to fit well with the observed data from four satellites during different universal times. This suggests that the electron flux obeys the power-law not only at the lower energies but also at the relativistic energies, and the KLU distribution may provide a better understanding of environments in those space plasmas where relativistic electrons are present.     

MOF衍生的Zn/N共掺杂碳催化剂的制备及其电催化性能

氮掺杂碳载非贵金属氧还原反应(ORR)催化剂已被广泛研究,以解决燃料电池Pt基催化剂的高成本问题.通过溶剂热法制备了无定形Zn基金属有机框架,并进一步经热处理得到Zn/N共掺杂碳催化剂.测试表明ZnN/C-900催化剂(热处理温度为900C)具有形貌均一的球形特征且比表面积高达961 m2·g-1,N、Zn的原子含量分...     

静电纺丝法制备的钴酸镍微米带的磁性以及电化学性能

通过直接退火静电纺丝前驱样品以及调节升温速率最终得到了钴酸镍(NiCo₂O₄)微米带. 通过X射线衍射、扫描电镜、振动样品磁强计以及电化学工作站等分析手段对钴酸镍微米带的晶体结构、形貌、磁学性能以及电化学性能进行了研究. 结果显示, 以1℃·min^-1的升温速率得到的NiCo₂O₄微米带属于立方尖晶石结构, 高温处理后仍能保持一维结构. 室温磁化结果显示制备的NiCo₂O₄微米带具有超顺磁性, 在10 kOe时磁化强度为6.35 emu·g^-1. 此外, 电化学测试结果显示, NiCo₂O₄微米带的电容特性是典型的赝电容, 并且比电容随着放电电流密度的增加而减小.     

Hydrolysis of flavonoid glycosides by propolis β-glycosidase

Flavonoids generally occur as O-glycosides with sugars bound in nature, while aglycones and their derivatives are the main flavonoids in propolis. The objective of this work was to study the propolis β-glycosidase activities toward flavonoid β-glycosides and their conjugated forms. β-Glycosidase was extracted from propolis, incubated with ?avonoid glycosides, and analysed for aglycone formation by HPLC. The results demonstrated that glucose conjugates were rapidly hydrolysed, but not conjugates with other sugars, i.e. rutin and naringin. The rate and extent of deglycosylation depends on the structure of the ?avonoid and the position of the sugar substituitions. Quercetin 3-O-glucoside had the highest percent of hydrolysis, while quercetin 7-O-glucoside was the least hydrolysed. The K(m) values for hydrolysis of apigenin 7-glucoside and luteolin-7-O-glucoside were 13 μM and 20 μM, respectively.     

石墨炉原子吸收法测定地表水中钡

在测定样品中加入适当的基体改进剂并控制工作条件及升温程序，可以快速、方便、准确地用石墨炉原子吸收法测定地表水中钡含量。     

Evolution of Ring Current Protons Induced by Electromagnetic Ion Cyclotron Waves

We investigate the evolution of the phase space density （PSD） of ring current protons induced by electromagnetic ion cyclotron （EMIC） waves at the location L=3.5, calculate the diffusion coefficients in pitch angle and momentum, and solve the standard two-dimensional Fokker-Planck diffusion equation. The pitch angle diffusion coefficient is found to be larger than the momentum diffusion coefficient by a factor of about 103 or above at lower pitch angles. We show that EMIC waves can produce efficient pitch angle scattering of energetic （- 100 keV） protons, yielding a rapid decrement in PSD, typically by a factor of - 10 within a few hours, consistent with observational data. This result further supports previous findings that wave-particle interaction is responsible for the rapid ring current decay.