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81.
Properties of excitons in vertically coupled GaAs/AlGaAs quantum dots were investigated using the variational method within the envelope function and effective mass approximations. It was found that when the thickness of the spacer layer becomes less than about one exciton Bohr radius, both the exciton binding energy and the fundamental optical transition energy are reduced compared to those in isolated quantum dots. This is a result of increased space extension of exciton due to the penetration of carrier wave functions into the spacer layer and corresponding reduction in confinement energy which dominates over the Coulomb interaction between the electron and the hole. 相似文献
82.
83.
复方单硝酸异山梨酯-阿司匹林双缓释微丸胶囊的研制(Ⅱ) 总被引:2,自引:0,他引:2
以乙基纤维素、丙烯酸树脂Ⅱ和丙烯酸树脂Ⅲ为骨架材料分别制备单硝酸异山梨酯和阿司匹林混合骨架缓释微丸,并通过包薄膜衣进一步控制药物的释放。通过测定微丸的释放度对处方工艺进行评价,选择最佳微丸灌装胶囊.胶囊中两种药物均达到良好的缓释效果。符合中国药典对缓释制剂的要求.其体外释放过程同时符合Higuchi方程和一级释药方程,R^2值均在0.995以上。 相似文献
84.
KunHuaLIN MaoPingSONG ChenXiaDU QiaoHongZHANG YangJieWU 《中国化学快报》2003,14(7):673-676
The cyclomercurated ferrocenylimines containing heterocyclic ring were prepared by the condensation of cyclomercuration of acylferrocene with the appropriate heterocyclic amine.This procedure provides an efficient method for the synthesis of cyclomerucurated ferrocenylimines containing heterocyclic ring which are difficultly synthesized by the conventional method.The reaction mechanism is proposed. 相似文献
85.
CAI Guang-Yu LlU Zhong-Min SHI Ren-Min HE Chang-Qing YANG Li-Xin SUN Cheng-LinDalian Institute of Chemical Physics Acadernia Sinica Dalian Iiaorting 《天然气化学杂志》1995,(2)
A new route named as SDTO method for the synthesis of lightolefins from syngas has been proposed.That is to convert syngas todimethylether and then to convert dimethylether to light olefins.The catalystsfor the two conversion reactions have been developed.For the first reaction,the catulySt was synthesized by the combination of methanol synthesis catalystwith γ-Al_2O_3or zeolites which possesses both metallic and acidic functions.Thecatalyst for the second reaction was modified SAPO-34 molecular sieve.Thevariables of the reactions have also been investigated.The results from theserial connection of the two conversion steps without any separation show thatthe yield of C_2~-C_4~- olefins Could be>100g/(m~3 syngas). 相似文献
86.
87.
BAHADURASYMPTOTICEFFICIENCYINASEMIPARAMETRICREGRESSIONMODEL¥LIANGHUA;CHENGPINGAbstract:TheauthorSgiveMLEθ1MLofθ1inthemodelY=θ... 相似文献
88.
以陆地棉(冀棉20)下胚轴为外植体,在含KT0.3mg/L和2,4-D0.08mg/L的MS培养基上,诱导产生了胚性愈伤组织,继代培养不需要添加激素,胚性愈伤组织即分化为胚状体,并萌发出小芽,胚状体萌发过程与合子胚相似,但出现了一些畸形胚,解剖学方法观察发现,这些畸形胚的维管束系统不明显或形态异常,以农杆菌介导法对冀棉20胚状体及胚性愈伤组织进行了雪花莲凝集素(GNA)基因的遗传转化条件探索,并以GUS基域瞬间进行检测加以证实,得出农杆菌的浓度为O.D600=0.8时,浸染时间为5min,共培养时间为3d,筛选培养基中卡那霉素浓度为75mg/L,对冀棉20胚状体及胚性愈伤组织转化是较为适合的。 相似文献
89.
Thin films of polystyrene (PS), poly(methyl methacrylate) (PMMA) and polystyrene-polyacrylonitrile copolymer (PS-AN), containing various embedded transition-metal complexes, have been studied by FTIR microscopy. The spatial distributions of the transition-metal carbonyl complexes throughout the thin organic polymer films have been determined by a two-dimensional IR mapping procedure. The spectral variations observed in the distribution of the metal carbonyls throughout the different polymer films are discussed. The IR data show that the technique used to prepare the organometallic-embedded thin films (viz. freeze-drying of solutions followed by hot mechanical pressing of the residues) does in general lead to homogeneous films which may eventually find industrial application, e.g. as membrane sensors for small molecules. 相似文献
90.
PENG Zi-cheng LI Ping ZHOU Tai-xi LI Xue-ming Wept. of Earth Space Science Univ. of Science Tech. of China Hefei )HU Zhi-sheng 《高等学校化学研究》1992,(3)
When was the earliest glass produced in China? This has still been a question so far. Some archaeologists have thought that Yu Guo beads are real glass, the earliest glass(1100-771 B. C. ) in China. However, more details of scientific investigations in this paper show that Yu Guo beads are mainly made of clastic quartz (>95%) with a small amount of clay and sintered under the low temperature(500-600℃). It is not a glassy body, but a kind of polycrystal ornaments. 相似文献