Two New Lignans from Taxus yunnanensis

The phytochemical investigation on the ethanolic extracts of the barks of Taxus yunnanensis (Taxaceae) led to the isolation of two new neo-lignans, named taxuyunins A (1) and B (2), along with the known diterpenolignan, brevitaxin (3). Their structures were elucidated on the basis of spectroscopic and chemical evidences. Compound 1 is a neo-lignan xyloside while compound 2 belongs to the rare neo-lignan possessing a ramified C3 side chain.     

13C核磁共振波谱法对高吸水性树脂交联反应的研究

UV光聚合法合成丙烯酸-丙烯酸钠共聚型高吸水性树脂(SAR)是一种新型的聚合方法,其中丙烯酸羟乙脂(HEA)是一种重要的交联剂。它通过共聚和酯化两种反应使聚合体系发生交联。通过~(13)C核磁共振波谱法(~(13)C-NMR)对交联体系进行分析,HEA在体系中的酯化交联率为22.3％,是使反应体系发生交联作用的主要原因。以HEA为交联剂制得的高吸水性树脂的吸水率Q可达996mL·g~(-1)。     

Role of Interactions in Electronic Structure of a Two-Electron Quantum Dot Molecule

We have studied a two-electron quantum dot molecule in a magnetic field. The electron interaction is treated accurately by the direct diagonalization of the Hamiltonian matrix. We calculate two lowest energy levels of the two-electron quantum dot molecule in a magnetic field. Our results show that the electron interactions are significant, as they can change the total spin of the two-electron ground state of the system by adjusting the magnetic field between S = 0 and S = 1. The energy difference AE between the lowest S = 0 and S = 1 states is shown as a function of the axial magnetic field. We found that the energy difference between the lowest S = 0 and S = 1 states in the strong-B S = 0 state varies linearly. Our results provide a possible realization for a qubit to be fabricated by current growth techniques.     

Influence of Growth Parameters of Frequency-Radio Plasma Nitrogen Source on Extending Emission Wavelengths from 1.31 μm to 1.55 μm GaInNAs/GaAs Quantum Wells Grown by Molecular-Beam Epitaxy

High （42.5%） indium content GaInNAs/GaAs quantum wells with room temperature emission wavelength from 1.3μm to 1.5μm range were successfully grown by Radio Frequency Plasma Nitrogen source assisted Molecular Beam Epitaxy, The growth parameters of plasma power and N2 flow rate were optimized systematically to improve the material quality. Photoluminescence and transmission electron microscopy measurements showed that the optical and crystal quality of the 1.54μm GaInNAs/GaAs QWs was kept as comparable as that in 1.31 μm.     

Hydrothermal Synthesis and Crystal Structure of a Cadmium(II) Polymer with One-dimensional Chain Structure: [Cd(bpy)(BDC)]_n·nbpy

A metal-organic coordination polymer [Cd(bpy)(BDC)]n·nbpy (bpy = 2,2-bipyri- dine, H2BDC = terephthalic acid) has been hydrothermally synthesized and structurally characteri- zed by elemental analysis, IR spectrum, TG and single-crystal X-ray diffraction. The complex crystallizes in monoclinic, space group C2/c with a = 15.723(5), b = 21.695(5), c = 7.576(5) , β = 116.171(7)o, V = 2319.3(18) 3, C28H20CdN4O4, Mr = 588.88, Dc = 1.686 g/cm3, μ(MoKα) = 0.987 mm-1, F(000) = 1184, Z = 4, the final R = 0.0464 and wR = 0.0831 for 1882 observed reflections (I > 2σ(I)). It exhibits a three-dimensional network with channels constructed from one-dimensional coordination chains via C–H···O hydrogen bonds and significant aromatic π-π stacking interactions.     

基于插入损耗的光纤信号调制器

基于光纤连接的横向偏移造成的插入损耗研制了一种的新型的光纤信号光调制器。调节对接光纤的横向偏移,可以调节对接光纤间的光耦合效率,利用调制信号调制横向偏移可实现对光纤传输光信号的调制。实验中,将调制电信号放大并加载于压电陶瓷使其振荡,由此控制对接光纤的横向偏移与调制信号同步变化,实现了对下一级光纤输出端光强的调制。这种光纤信号调制器主要针对光的振幅调制,实验中获得调制度优于95%,信噪比约为20dB,带宽约为200kHz。具有价格低廉、调制度高的特点,可应用于光纤传输信号的调制及信号斩波等。     

Microstructure and Corrosion Performance of Oxide Coatings on Aluminium by Plasma Electrolytic Oxidation in Silicate and Phosphate Electrolytes

Ceramic coatings are fabricated on pure aluminium by plasma electrolytic oxidation （PEO） in three kinds of electrolyte systems [E1： 0.05M NaOH＋0.033M Na2SiO3, E2： 0.025M NaOH＋0.008M （NAPO3）6 and E3： 0.025M NaOH＋0.066M Na2SiO3＋0.008M （NAPO3）6]. The voltage-time responses show that the PEO process of E2 has the highest discharging voltage, which results in the biggest pores and heaviest cracks on the surfaces. X-ray diffraction results show that coatings produced in E1 and E3 are mainly composed of γ-Al2O3 and mullite, while coatings produced in E2 are mainly composed of a-Al2O3. After PEO treatment the corrosion resistance of aluminium is improved significantly and the coatings produced in E3 perform the best corrosion resistance.     

Carnot群上一类半线性方程的Liouville型定理

本文研究了Carnot群上一类具有超线性非齐次项的半线性次Laplace方程非负解的存在性问题.结合Birindelli等[4]在Heisenberg群上利用积分不等式研究解的方法和拟齐性分析技巧,给出了此类方程在Carnot群上的一类Liouville型定理.     

二元混合染料在SiO2凝胶膜中的发光光谱

在SiO2凝胶材料中掺杂香豆素102和若丹明6G混合染料后,二元染料之间存在着能量传递,其发光光谱比单一染料的光谱展宽.前者在SiO2凝胶基质中可调谐范围展宽到120 nm,混合染料在SiO2凝胶基质中发光光谱展宽,并且具有更高的能量转移效率.     

GdF_3∶Eu~(3+)纳米晶的VUV荧光性质

利用微乳液水热法制备出GdF3∶Eu3+纳米晶及纳米棒。用X射线粉末衍射(XRD)和透射电子显微镜(TEM)等手段对材料的结构、形态及粒径大小等进行了表征。室温下真空紫外(VUV)光谱及荧光光谱表明GdF3∶Eu3+纳米晶中的Gd3+离子吸收一个光子,并将能量分两步传递给Eu3+,发生了双光子发射。从各跃迁的积分强度和量子效率表达式可以得到材料在160 nm紫外光激发下的量子效率约为170%。