十二烷基苯磺酸钠(DBS)对原生动物的毒性效应

进行了十二烷基苯磺酸钠(DBS)对原生动物的种、种群和群落等三个不同生物学组织水平的毒性试验。结果表明:DBS对5种原生动物的急性毒性作用没有种的特异性(p>0.05)。半致死浓度12h-LC_(50)在7.0—10.47ppm之间;对美洲四膜虫种群的急性毒性作用,12h—LC_(50)为17.21ppm;对其呼吸率的影响,表明其效应浓度为12.84ppm(p<0.05);3—40ppm DBS,对微型生物群落的结构、功能有不同程度的影响。结构参数有原生动物种类组成和种类数;功能参数有原生动物群集过程、微

A widely tunable continuous-time LPF for a direct conversion DBS Tuner

A continuous-time 7th-order Butterworth Gm-C low pass filter (LPF) with on-chip automatic tuning circuit has been implemented for a direct conversion DBS tuner in a 0.35um SiGe BiCMOS technology. The filter's -3dB cutoff frequency f(0) can be tuned from 4MHz to 40MHz. A novel translinear transconductor (Gm) cell is used to implement the widely tunable and high linear filter. The filter has -0.5dB passband gain, 28nV/Hz(1/2) input referred noise, -2dBVrms passband IIP3, 24dBVrms stopband IIP3. The I/Q LPFs with the tuning circuit draw 16mA (with f(0)=20MHz) from 3.3 V supply, and occupy an area of 0.45 mm(2).

A widely tunable continuous-time LPF for a direct conversion DBS tuner

A continuous-time 7th-order Butterworth Gm-C low pass filter (LPF) with on-chip automatic tuning circuit has been implemented for a direct conversion DBS tuner in 0.35μm SiGe BiCMOS technology. The filter's -3 dB cutoff frequency f0 can be tuned from 4 to 40 MHz. A novel on-chip automatic tuning scheme has been successfully realized to tune and lock the filter's cutoff frequency. Measurement results show that the filter has -0.5 dB passband gain, +/- 5% bandwidth accuracy, 30 nV/Hz~(1/2) input referred noise, -3 dBVrms passband IIP3, and 27 dBVrms stopband IIP3. The I/Q LPFs with the tuning circuit draw 13 mA (with f_0 = 20 MHz) from 5 V supply, and occupy 0.5 mm~2.

Sudies on non-isothermal melt crystallization kinetics in PET/PEN/DBS blends

Macrokinetic models, namly the modified Avrami, Ozawa and Zibicki models, were applied to study the non-isothermal melt crystallization process of PET/PEN/DBS blends by DSC measurement. The modified Avrami model was found to describe the experimental data fairly well. With the cooling rates in the range from 5 to 20 K/min, Ozawa model could be well used to describe the early stages of crystallization. However, Ozawa model did not fit the polymer blends during the late stages of crystallization, because it ignored the influence of secondary crystallization. The crystallization ability of the blends decreases with increasing the DBS content from analysis by using Ziabicki kinetic model, which is similar to the results based on calculation of the effective energy barrier of the blends.

Photoluminescence of Er-doped hydrogenated amorphous silicon nitride

Er photoluminescence (Er PL) and dangling bonds (DBs) of annealed Er-doped hydrogenated amorphous silicon nitride (a-SiN:H(Er)) with various concentrations of nitrogen are studied in the temperature range 62-300 K. Post-annealing process is employed to change the DBs density of a-SiN:H(Er). PL spectra, DBs density and H, N concentrations are measured. The intensity of Er PL displays complicated relation with Si DBs density within the annealing temperature range 200-500 degreesC. The intensity of Er PL first increases with decreasing density of Si dangling bonds owing to the structural relaxation up to 250 degreesC, and continues to increase up to 350 degreesC even though the density of Si DBs increases due to the improvement of symmetry environment of Er3+. (C) 2003 Elsevier B.V. All rights reserved.

有序纳米薄膜的组装及其结构研究

纳米材料具有一系列新异的物理、化学特性，但是纳米粒子只有组装特定的结构才能制成器件应用于实际。本论文的目标就是制备多种具有特定结构的周期性有序的纳米薄膜，探索化学方法制备各种有机－无机、无机－无机超晶格结构的途径。首次通过布儒斯特角显微镜，观察到了 SnO_2、Fe_2O_3 及 TiO_2 等无机氧化物纳米溶胶在其与空气的界面上能自发成膜的现象，并进一步对 SnO_2 纳米溶胶界面所形成的界面膜进行了详细研究，发现在空气与 SnO_2 纳米溶胶界面形成稳定的界面膜约需 8 h，膜厚约为 20 nm，垂直方式转移的膜质量比较好，膜的组成为非化学计量比的 SnO_(2-x)，其中存在着大量的氧空位。虽然随着在空气中放置时间的增长，发现转移出来的膜不很稳定，膜中粒子有长大的倾向，但是薄膜始终处于纳米量级，而且这种方法操作简单、适于规模化生产，因此仍不失为一种制备无机氧化物纳米薄膜的方法。为了达到使纳米粒子稳定和有序化的双重目的，制备了花生酸掺杂的 DBS 包裹的 SnO_2 纳米有机溶胶，并采用 LB 技术对其进行了组装。发现花生酸掺杂的 SnO_2 纳米粒具有很好的成膜性，崩溃压可达 60 mN/m，可以成功地往固体基片上转移上百层，转移比均在 0.8-1.0 之间。转移膜的红外光谱、紫外光谱及 X 光电子能谱的研究表明，转移多层膜的组成为 SnO_2 和花生酸，包裹 SnO_2 纳米粒子的 DBS 为花生酸所代替而溶于亚相水中。转移膜非常均匀，由 100 nm 左右的畴构成，畴由更小的粒子组成。偏振红外光谱和小角 X 射线衍射的研究表明花生酸在膜中是取向排列的，碳链与其法线约成 10.2°夹角，SnO_2 纳米粒子和花生酸形成了交替重复的周期性结构，其周期间距为 7.48 nm。采用同样方法，还成功地组装了 TiO_2 纳米粒子和花生酸交替重复的周期性有序结构。进一步对花生酸掺杂的 TiO_2 纳米粒子和 SnO_2 纳米粒子进行了交替组装，发现交替膜是由 SnO_2、TiO_2 和花生酸组成的，花生酸在膜中取向排列，其碳链与法线的夹角为 36°，SnO_2 纳米粒子、TiO_2 纳米粒子和花生酸形成了一种有机物质和两种无机纳米粒子交替重复的 SnO_2－花生酸－TiO_2－花生酸的周期性有序结构，其周期间距为 6.46 nm。得到了几种准一维的有机－无机超晶格结构并找到了制备它们的化学方法。对所得的 SnO_2－花生酸和 SnO_2－花生酸－TiO_2－花生酸的周期性有序结构直接进行了热处理，并对组合体的变化进行了研究。发现热处理后，膜中的有机成分完全分解，前者的周期性结构遭到彻底破坏，但是却得到了沿 (101)晶面取向的 SnO_2 薄膜；后者的周期性结构经过一系列的变化，却依然保持，形成了 SnO_2 纳米粒子和 TiO_2 纳米粒子交替重复的周期性有序结构。开辟了一条采用化学方法制备准一维的无机－无机超晶格材料的途径。成膜物质在亚相表面形成稳定的单层膜的条件和单层膜向固体基片的转移条件是制备高质量 LB 膜的关键，重点对花生酸在 YCl_3 稀溶液表面的成膜行为进行了研究，发现亚相的 pH 值和溶剂的挥发时间对单分子膜的形成都具有很大影响，所形成的单分子膜在该亚相表面是不可逆的。进一步研究了单层膜的转移条件，并选定最佳条件将单分子膜转移到固体基片上，对膜的组成、形貌等进行了多种表征测试。发现我们得到了是结构非常好的含有三个链的花生酸钇 M(AA)_3 的 Y－型的周期性结构，碳链在膜中与基底法线的夹角为 28.5°，而不是有的文献认为的羟基化的花生酸钇 M(AA)_2OH LB 膜。

DENSITY-OF-STATES OF THE 2-DIMENSIONAL ELECTRON-GAS STUDIED BY MAGNETOCAPACITANCES OF BIASED DOUBLE-BARRIER STRUCTURES

The magnetocapacitive response of a double-barrier structure (DBS), biased beyond resonances, has been employed to determine the density of states (DOS) of the two-dimensional electron gas residing in the accumulation layer on the incident side of the DBS. An adequate procedure is developed to compare the model calculation of the magnetocapacitance with the experimental C vs B curves measured at different temperatures and biases. The results show that the fitting is not only self-consistent but also remarkably good even in well-defined quantum Hall regimes. As a result, information about the DOS in strong magnetic fields could reliably be extracted.

Self-consistent calculation of electronic states in asymmetric double barrier structure

With contributions from both three-dimensional (3D) electrons in heavily doped contacts and 2D electrons in the accumulation layer, a self-consistent calculation based on effective mass theory is presented for studying the anomalous behaviour of the quasi-bound levels in the accumulation layer and that in the central well of an asymmetric double barrier structure (DBS). By choosing the thickness of the incident barrier properly, it is revealed that these two quasi-bound levels may merge into a unique bound level in the off-resonance regime which shows a very good 2D nature in contrast to the conventional picture for level crossing. An evident intrinsic I-V bistability is also shown. It is noticeable that the effect of charge build-up in the central well is so strong that the electric field in the incident barrier even decreases when the applied bias increases within the resonant region.

磁隧穿振荡研究GaAs/AlAs双势垒结构中的Г-X电子态混合

报道了非对称GaAs/AlAs双势垒结构(DBS)中的Γ-X-Γ磁隧穿振荡现象,用磁场倒数周 期求得AlAs层中X谷和GaAs层中Γ谷之间的能带不连续值与通常公认值符合很好.良好的 振荡特性可作为定量研究Γ-X耦合强度的灵敏的实验办法.

非对称双势垒结构中电子态的特异性

在包络波函数近似下自洽计算了非对称双热垒结构(DBS)中的电子态,并正确得到了积累区和中央势阱中准束缚能级E_(ac)、E_(we)随偏压变化的反交叉过程.结果首次揭示了结果适当选取DBS的入射垒厚度,随着外加电场不断增加,在过共振区积累层势阱和中央势阱会统一成一个大三解势阱的基态能级E_(com),E_(com)具有很好的二维性,这表明在过共振区DBS在入射端积累区中只存在二维电子.

成核剂1,3:2,4-二(亚苄基)-D山梨醇对PET/PEN共混体系结构和结晶形态影响

利用差示扫描量热仪、X射线衍射仪、正交偏光显微镜研究了成核剂 1,3 :2 ,4-二 (亚苄基 ) -D山梨醇(DBS)对聚对苯二甲酸乙二醇酯 (PET) /聚 2 ,6-萘二甲酸乙二醇酯 (PEN)共混体系的结构及结晶形态的影响。结果表明 :成核剂的加入 ,使PET/PEN共混体系熔融起始温度升高 10℃左右 ,结晶峰形变尖锐 ,说明加入成核剂后有效促进了PET/PEN共混体系的结晶。实验结果表明 :成核剂含量低于 1%时 ,PET/PEN共混体系晶体的球晶完整。成核剂含量大于 3 %时 ,PET/PEN /DBS共混体系晶体的球晶碎小。成核剂的加入 ,能够有效地减小球晶尺寸和降低球晶的完善性

Synthesis and characterization of hyperbranched poly(ester-amide)s from commercially available dicarboxylic acids and multihydroxyl primary amines

A new method for syntheses of hyperbranched poly(ester-amide)s from commercially available A(2) and CBx type monomers has been developed on the basis of a series of model reactions. The aliphatic and semiaromatic hyperbranched poly(ester-amide)s with multihydroxyl end groups are prepared by in situ thermal polycondensation of intermediates obtained from dicarboxylic acids (A(2)) and multihydroxyl primary amines (CBx) in N,N-dimethylformamide. Analyses of FTIR, H-1 NMR, and C-13 NMR spectra revealed the structures of the polymers obtained. The MALDI-TOF MS of the polymers indicated that cyclization side reactions occurred during polymerization. The hyperbranched poly(ester-amide) s contain configurational isomers observed by C-13 and DEPT C-13 NMR spectroscopy. The DBs of the polymers were determined to be 0.38-0.62 by H-1 NMR or quantitive C-13 NMR and DEPT 135 spectra. These polymers exhibit moderate molecular weights, with broad distributions determined by size exclusion chromatography ( SEC), and possess excellent solubility in a variety of solvents such as N, N- dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, and ethanol, and display glass-transition temperatures (T(g)s) between -2.3 and 53.2 degrees C, determined by DSC measurements.

透明纳米CeO_2的合成与表征

采用胶溶法合成了表面修饰十二烷基苯磺酸钠 (DBS)的CeO2 纳米粒子有机溶胶。探讨了制备CeO2 纳米有机溶胶的最佳实验条件。TEM分析表明 ,CeO2 (DBS)纳米粒子呈球形 ,约 3nm ,粒径分布均匀 ,无团聚现象。ED分析表明 ,CeO2 (DBS)纳米粒子为多晶结构。

PREPARATION AND MICROSTRUCTURAL CHARACTERIZATION OF SURFACE-MODIFIED NANOSIZED SNO2 PARTICLES

Nanosized stannic oxide particles modified with a layer of DBS were successfully prepared through the colloidal chemical method and their microstructures were characterized. FTIR and XPS were used for the determination of the main components. It can be proved that the nanosized SnO2 particles were capped by DBS. The sizes of particle were determined by TEM and XRD. By the investigation of XPS, we can conclude that there are a lot of oxygen vacancies in the surface of the nanoparticulates. Based on this conclusion, the ESR signal of the sample can be explained.