Theoretical STM images of alkaline-earth metal adsorbed Si(1 1 1)3 × 2 surfaces

We have performed total-energy calculations to study theoretical scanning tunneling microscopy (STM) images of the Si(1 1 1)3 × 2 surfaces induced by the adsorption of alkaline-earth metals (AEMs). Previously, in a series of works on Ba/Si(1 1 1) system, we have found that the observed Si(1 1 1)3 × 1-Ba LEED phase indeed has a 3 × 2 periodicity with a Ba coverage of 1/6 ML and the HCC substrate structure. Based on results of the Ba case, we proposed that the HCC structure is also adopted for other AEM atoms, which was confirmed by our recent work. In this paper, we mainly report the STM simulations for different AEM systems to compare with existing experimental data. We discuss the difference in the detailed STM images for different AEM adsorbates. Especially, the difference in filled-state images between Mg and other AEM atoms is attributed to the strong Mg-Si interaction.     

40Ar+诱导无定形碳到金刚石纳米晶相变的研究

通过60 keV的⁴⁰Ar⁺辐照无定形碳靶合成了大量尺寸不同的金刚石纳米颗粒.高分辨透射电子显微镜配合能量色散X射线谱和电子衍射以及Raman谱分析的结果表明，这些嵌于具有扰动石墨结构薄膜中的纳米金刚石颗粒，其成核率很高(约为10¹³/cm²)，而且可以生长到较大的尺寸，有的甚至可以达到微米量级.对其相转变过程也进行了初步探讨. 关键词： 离子束 金刚石纳米晶 相变 透射电子显微镜     

一种基于功率谱对数变换的联合变换相关器

联合功率谱的高频成份对相关峰识别具有重要作用,实验中记录的联合功率谱随着频率的增加其强度迅速降低。为增强联合功率谱的高频成分,改善其调制程度,可对功率谱进行对数变换,从而有效保留更多的高频成份,压低零级衍射光斑,提高联合变换相关器的识别能力。     

无催化纳米氧化锌的制备及其光学性质研究

本文采用无催化剂直接蒸发高纯Zn粉,在800℃氧气氛条件下,在Si(111)衬底上生长得到以四角状为主的纳米ZnO(T-ZnO)。T-ZnO纳米线每个角约互成110°,长度约为1.5μm,直径100nm左右;Raman分析表明E2(H)普遍存在于各形态的ZnO;光致发光光谱表明,T-ZnO纳米线的光致发光除了与材料性质有关,还与杂质缺陷有关,蓝绿光带是ZnO的缺陷产生的。     

非齐次微分方程两点边值问题正解的存在性及多重性

本文考虑一类非齐次微分方程的两点边值问题,得到了一些有关其正解存在性与多重性的精确条件．     

High-pressure effect on the crystal and magnetic structure of LuMnO3: Correlation between a distortion of the triangular lattice and the symmetry of the magnetic state in hexagonal frustrated manganites

The effect of a high pressure (up to 6 GPa) on the crystal and magnetic structure of the hexagonal manganite LuMnO₃ is studied by neutron diffraction in the temperature range 10–295 K. It is found that, as the pressure increases, the ordered magnetic moment of Mn ions at T = 10 K decreases noticeably from 2.48 (0 GPa) to 1.98 μ_B (6 GPa). This decrease is due to an enhancement of the geometrical frustration effects on the triangular lattice. At the same time, the symmetry of the triangular antiferromagnetic state (the irreducible representation Γ₂) remains unchanged. A correlation is revealed between the distortion parameter of the triangular lattice formed by Mn ions and the symmetry of the antiferromagnetic state of hexagonal manganites RMnO₃. Based on this correlation, a generalized magnetic phase diagram of these compounds is constructed. The obtained phase diagram provides an explanation for the changes observed in the magnetic state of hexagonal manganites caused by high pressure and chemical substitution.     

Surface free energy of CrNx films deposited using closed field unbalanced magnetron sputtering

CrN_x thin films have attracted much attention for semiconductor IC packaging molding dies and forming tools due to their excellent hardness, thermal stability and non-sticking properties (low surface free energy). However, few data has been published on the surface free energy (SFE) of CrN_x films at temperatures in the range 20-170 °C. In this study CrN_x thin films with CrN, Cr(N), Cr₂N (and mixture of these phases) were prepared using closed field unbalanced magnetron sputtering at a wide range of Cr⁺² emission intensity. The contact angles of water, di-iodomethane and ethylene glycol on the coated surfaces were measured at temperatures in the range 20-170 °C using a Dataphysics OCA-20 contact angle analyzer. The surface free energy of the CrN_x films and their components (e.g., dispersion, polar) were calculated using the Owens-Wendt geometric mean approach. The influences of CrN_x film surface roughness and microstructure on the surface free energy were investigated by atomic force microscopy (AFM) and X-ray diffraction (XRD), respectively. The experimental results showed that the lowest total SFE was obtained corresponding to CrN at temperature in 20 °C. This is lower than that of Cr(N), Cr₂N (and mixture of these phases). The total SFE, dispersive SFE and polar SFE of CrN_x films decreased with increasing surface temperature. The film roughness has an obvious effect on the SFE and there is tendency for the SFE to increase with increasing film surface roughness.     

燃煤循环流化床燃烧脱硫的模型预测

燃煤循环流化床燃烧脱硫的模型预测池涌，岑可法，倪明江Ｐ·Ｂａｓｕ（浙江大学能源系杭州３１００２７）关键词：循环流化床，燃烧，脱硫，模型预测一、引言循环流化床锅炉在过去十几年中得到了广泛的应用，但与此同时由于循环流化床内流体动力特性的高度复杂使得数学模...     

Fluorescence anisotropy decay study of self-association of bacterial luciferase intermediates

The fluorescence dynamics parameters of the fluorescent transient flavin-luciferase species from the typesVibrio fischeri andPhotobacterium leiognathi are presented. The fluorescence anisotropy decay is a single exponential function for both types. The correlation time is 70 ns for theP. leiognathi fluorescent transient intermediate (2°C, aqueous buffer, pH 7.0), consistent with the rotational correlation time of the luciferase macromolecule (77 kD) to which the flavin fluorophore is rigidly attached. In contrast, for theV. fischeri species the observed correlation time for the anisotropy decay function is 133 ns. This suggests that protein self-association occurs in theV. fischeri case and this is confirmed by filtration, where the fluorescent transient fromV. fischeri does not pass through a 100,000 molecular weight cutoff membrane, whereas theP. leiognathi species does. The filtration method also demonstrates self-association in the luciferase peroxyflavin and photoflavin fromV. fischeri. A monomer-dimer equilibrium also explains the previously reported high correlation times for theV. harveyi luciferase-flavin species. It is proposed that the self-association competes with the lumazine protein interaction in the bioluminescence reaction.     

影响海洋微藻生产麻痹性贝类毒素的重要生态因素

麻痹性贝类毒素是有害赤潮海洋微藻生产的重要毒素种类，本文综述了影响该类毒素的主要生态因素有光，温度，盐度和营养盐4类；弱光对毒素合成有抑制作用。低温下PSP毒素产量高，通过对营养盐吸收机制的离子效应，盐度可影响毒素的生命合成，不同种类和株系对N、P限制的反应有极大差异。