A theoretical model for the tilt of the GaAs/Si epilayers

The crystallographic tilt of the epilayers with respect to their substrates has been observed in many heteroepitaxial systems. Many models have been proposed to explain this phenomenon, but none of them is suitable for the large mismatched system, such as GaAs/Si. Here a new model is proposed for GaAs/Si epilayers, which can also be used in other large mismatched systems. The magnitude of the tilt calculated from this model coincide well with the experimental results. Especially, this model can correctly predict the tilt direction of the GaAs/Si epilayers.

GaN基紫外探测器及其研究进展

宽禁带半导体材料的研究和突破,带动了各种器件的发展和应用.GaN基紫外探测器具有通过调整材料的配比可以调节器件响应的截止波长的优点,可以制备日盲型紫外探测器.对GaN基宽禁带紫外探测器材料体系的研究进展进行了回顾,重点介绍了p型材料的制备、金属半导体接触、材料的蚀刻等.最后,对国内外近期的紫外探测器特别是紫外焦平面器件的研究进展及初步获得的32×32紫外焦平面探测器进行了简单介绍.

合成食用色素柠檬黄选择性电极的研制和应用

本文研究了以十二烷基三庚基碘化铵-柠檬黄缔合物为活性材料的PVC膜电极和涂丝电极,两电极对柠檬黄浓度在1.0×10~(-6)～1.0×10~(-3)mol/L间的响应符合Nernst关系式,斜率为20.0±1.0mV/PC(22℃),pH范围为4.0～9.4,电极的选择性、重现性和稳定性良好。对样品的测定结果与分光光度法测定结果基本一致。该方法简便、准确、可靠。

稀土对Al—Mg—Si合金晶体结构参数的影响

在研究和探索稀土对铝合金作用机理的过程中,稀土的良好作用已为越来越多的研究所证实。目前,有关稀土对铝合金宏观组织和性能影响的研究报道较多,但有关稀土对铝合金晶体结构参数的影响报道很少。本文研究了稀土对Al-Mg-Si合金晶体结构参数的影响,可以说,稀土能够提高铝合金的机械性能,在宏观组织上表现为晶粒细化,在微观结构上表现为晶胞参数变小。

THERMODYNAMICS OF COMPLEXATION OF RARE EARTHS BY L-METHIONINE

The protonation constant of the ligand and stability constants of it complexes with rare earths have been determined by potentiometric titration at 25 degrees C and ionic strength mu=0.15 mol - L-1. The results indicate that rare earth elements can form 1:1 complexes with L methionine. There is an apparent "tetrad effect" in this system. Shift of the yttrium position to the vicinity of Gd can he explained by the different polarisation between the Ln(3+) and the ligand. The enthalpy changed (Lambda H-101) of the coordination reaction as represented by the reaction (M + L (sic) ML) here been measured by calorimetric titration, where M and L. denote are eartus and L-Mer respectively. The Lambda G(101) and Delta S-101 of these reaction have been calculated by using Gibbs' equation, Furthermore, the stability of rare earth complexes with L-Met has been compared with that of Ca3+ Zn3+, Fe2+, Fe3+ complexes with L-Met.

稀土离子选择电极活性材料的研究

我们曾经研究了功能高分子活性材料的稀土离子选择电极。然而至今尚未见到这种活性材料的制备方法以及电极膜中稀土离子价态方面的报道。本文报导了这一方面的研究结果。

稀土-蛋氨酸配合物的热力学

在25℃和μ=0.15mol·L~(-1)[NaCl]条件下,用pH电位法测定了L-蛋氨酸的质子化常数、15个稀土元素与该配体生成配合物的稳定常数。表明稀土与L-蛋氨酸可生成1:1配合物。讨论了“四分组效应”及钇的位置。用量热滴定法直接测定了稀土与L-蛋氨酸生成1:1配合物的△H_(101)值,计算了△S_(101)和△G_(101)值。

Molecular phylogenetic analysis of attached Ulvaceae species and free-floating Enteromorpha from Qingdao coasts in 2007

Based on the sequence data of the nuclear ribosomal DNA internal transcribed spacer (ITS) 1, 5.8 S, and ITS 2, the molecular phylogeny was analyzed on Ulvaceae species collected from Qingdao coasts in summer of 2007, including 15 attached Ulva and Enteromorpha samples from 10 locations and 10 free-floating Enteromorpha samples from seven locations. The result supported the monophyly of all free-floating Enteromorpha samples, implying the unialgal composition of the free-floating Enteromorpha, and the attached Ulvaceae species from Qingdao coasts were grouped into other five clades, suggesting that they were not the biogeographic origin of the free-floating Enteromorpha in that season.