Polysilsesquioxane Nanosheets Synthesized in Confined Environment

Polysilsesquioxane nanosheets with a thickness of four nanometers and lateral dimensions of several hundreds of nanometers were synthesized by polymerization of a trifunctional monomer in the layer space of montmorillonite as the confined environment.

AFM image of a polymethylsilsesquioxane nanosheet.     

焙烧温度对Mg(Al)O复合物结构和表面酸碱性质影响的研究

分别在673、873和1073K分解Mg/Al摩尔比为3的水滑石生成Mg(Al)O复合物.XRD测定均显示MgO物相.873K以上焙烧的样品同时存在MgAl2O4尖晶石物相.微量吸附量热测定其表面酸碱中心的强度和密度,发现碱中心强度和密度顺序为:MAO-2＞MAO-3≈MAO-1,而酸中心强度和密度顺序是:MAO-1＞MAO-3≈MAO-2.红外光谱表明,Mg(Al)O复合物表面酸碱中心主要存在L酸,碱中心是氧阴离子.焙烧温度对表面碱中心类型几乎没有影响.固态MAS27Al核磁共振结果展示,这些样品呈现出显著的Al3+配位情况的变化.     

ACCURATE DETERMINATION OF FILM THICKNESS BY LOW-ANGLE X-RAY REFLECTION

A modified Bragg law for straightforward determining the film thickness by low-angle X-ray reflection was derived based on the geometrical optical theory. We showed that this modified Bragg law and its inference formulae could be used to accurately determine the thickness of the monolayer or multilayer film. Furthermore, the modified Bragg law for determining the superlattice period presented earlier by others can be derived from the above modified Bragg law. The similar inference formulae were also given. The precision in determining the film thickness and/or superlattice period by the above formulae was discussed.     

纳米级介孔分子筛及其超分子发光功能材料的制备与表征

本文在超声波条件下以三甲基十六烷基溴化铵为模板剂,正硅酸乙酯为硅源合成了纳米级（10－40nm)的介孔分子筛（MCM－41）,其筛孔直径在2．7nm左右,选择Eu(Phen)4为客体,纳米级介孔分子筛为主体,在无水乙醇中进行分子组装,制备具有强发光性能的超分子纳米材料MCM－41－Eu(Phen),采用HRTEM,TEM,XRD,TG,IR和荧光光谱检测手段对产物进行了表征。     

人脑初级视皮层内事件相关型视觉刺激fMRI BOLD响应特性初步研究

基于脑血氧水平依赖(BOLD)对比的功能磁共振成像（fMRI）方法是研究脑功能活动的一种重要的无损伤探测手段，BOLD的机制及它与脑神经活动关系一直是国际上十分活跃的研究领域，尤其是在实验研究方面. 视觉刺激所引起的脑的初级视皮层(V1) 的BOLD响应的时间特性已有较多的研究，但是在这些研究中，有的结论认为BOLD对视觉刺激的响应是线性的，有的结论却是相反的. 我们采用事件关联型核磁共振功能成像（ER-fMRI）方法，研究不同的短暂视觉刺激持续时间下的BOLD响应，得到了视觉刺激下的脑激活图. 同时找出了视觉刺激时间分别是1、2、3、4、5和6 s的V1区的BOLD响应曲线，并初步显示出BOLD响应与刺激持续时间的线性关系.     

对碘酚对鲁米诺化学发光增强的试验研究

本文报道了由过氧化物酶催化鲁米诺与过氧化氢发光反应的增强发光研究。合成了增强剂对碘酚,并用对碘酚对鲁米诺与过氧化氢发光反应的光增强作用进行了试验,已经证实增强发光反应可将过氧化物酶的最低检测浓度降低到10-12～10-13mol/L水平。     

Impact‐specific essential work of fracture of maleic anhydride‐compatibilized polypropylene/elastomer blends and their composites

Charpy drop‐weight‐impact and essential work of fracture (EWF) characteristics of maleic anhydride (MA)‐compatibilized styrene–ethylene butylene–styrene (SEBS)/polypropylene (PP) blends and their composites reinforced with short glass fibers (SGFs) were investigated. MA was grafted to either SEBS copolymer (SEBS‐g‐MA) or PP (PP‐g‐MA). The mPP blend was prepared by the compounding of 95% PP and 5% PP‐g‐MA. Drop‐weight‐impact results revealed that the mPP specimen had an extremely low impact strength. The incorporation of SEBS or SEBS‐g‐MA elastomers into mPP improved its impact strength dramatically. Similarly, the addition of SEBS was beneficial for enhancing the impact strength of the SGF/SEBS/mPP and SGF/SEBS‐g‐MA/mPP hybrids. A scanning electron microscopy examination of the fractured surfaces of impact specimens revealed that the glass‐fiber surfaces of the SGF/SEBS/mPP and SGF/SEBS‐g‐MA/mPP hybrids were sheathed completely with deformed matrix material. This was due to strong interfacial bonding between the phase components of the hybrids associated with the MA addition. Impact EWF tests were carried out on single‐edge‐notched‐bending specimens at 3 m s^?1. The results showed that pure PP, mPP, and the composites only exhibited specific essential work. The nonessential work was absent in these specimens under a high‐impact‐rate loading condition. The addition of SEBS or SEBS‐g‐MA elastomer to mPP increased both the specific essential and nonessential work of fracture. This implied that elastomer particles contributed to the dissipation of energy at the fracture surface and in the outer plastic zone at a high impact speed of 3 m s^?1. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1881–1892, 2002     

Diffusion tensor image up-sampling: a registration-based approach

Diffusion weighted images (DWI), from which the corresponding diffusion tensor images (DTI) are estimated, are commonly acquired with anisotropic discretizations. Traditional methods to up-sample diffusion weighted images generally rely on scene-based interpolation and do not exploit structural information from the images. In this study, a DTI up-sampling framework is presented that incorporates the underlying anatomical shape information by means of non-rigid inter-slice registration. A strategy is proposed to reorient the interpolated tensor in order to maintain its proper orientation. Tests on phantom as well as on real data sets show that the proposed method is able to produce better results compared to scene based interpolation methods in terms of the accuracy of DWI/DTI interpolation, especially when diffusion tensor orientation is taken into account.