Functionalization of Scanning Force Microscopy Cantilevers via Galvanic Displacement Technique

A galvanic displacement technique is used to coat silicon scanning force microscopy cantilevers with copper. The copper coating is characterized using X-ray photoelectron spectroscopy, scanning force microscopy, contact angle measurements, scanning electron microscopy and energy-dispersive X-ray spectroscopy. This coating technique results in uniform, reflective and conformal films and hence, no stress-induced bending of the cantilever is observed. To demonstrate the effectiveness of this approach for tribological studies, the coated cantilevers are chemically modified with alkanethiol monolayers in order to functionalize the cantilevers. The effect of changed surface energy are detected with adhesion measurements in water and ethanol.     

利用格氏反应制备多氟乙烷类液晶的新方法

以4-氯甲基-4′-正烷基-1,1-双环己烷与3,4,5-三氟苯腈为原料,通过格氏反应合成中间体酮,再经黄鸣龙还原得多氟乙烷类液晶化合物,总收率≥160％。     

流态化模拟:基于介尺度结构的多尺度CFD

介尺度结构是研究气固流态化多尺度行为的关键。传统的基于平均化处理方式的双流体模拟不能准确描述流化床中的多尺度流动和传递行为。相较而言,基于能量最小多尺度(EMMS)方法的结构多流体模型(SFM)基于局部空间(网格)内的非均匀介尺度结构流动特征,其宏观预测结果与网格分辨率基本无关,因而可以大幅降低模拟计算量。基于SFM模拟得到的流动结构,EMMS多尺度传质模型进一步成功解释了传统传质文献中的数据差异。集成上述模型,形成了一整套模拟流化床流动-传递-反应耦合过程的多尺度计算流体力学(CFD)方法,并将其应用于预测循环流化床中典型的S型轴向分布、揭示噎塞转变的机理以及流化床放大困难的原因。多尺度CFD使工业规模循环床的三维、全系统、动态流动-反应耦合过程的准确模拟成为可能,并为实现从模拟向实时虚拟过程转变的目标打下基础。     

基于广义周期性的单通道多分量正弦调频信号分离和参数估计

针对噪声条件下的单通道多分量正弦调频(SFM)信号,该文提出一种信号分离和参数提取方法。利用正弦调频信号的广义周期性进行奇异值分解,以求出分量信号的调制频率;通过离散点搜索,估计出分量信号的调频(FM)初始相位、调制指数及载频,并对这些估计值利用信赖域算法进行优化,减小误差;利用内积计算,估计分量信号的幅度和初始相位。此外,还利用自相关矩阵特征值分解估计混合信号的信噪比(SNR),并根据信噪比确定停止分解的阈值。在仿真与分析中,针对具体的信号详细说明了该方法的各步骤,并在不同信噪比条件下分析了该方法的参数估计精确度。     

A metrological scanning force microscope

In this paper, the design, construction, and characterization of a metrological scanning force microscope (SFM) for the purposes of dimensional measurement of surface features is discussed. Using this instrument, precision measurements of engineering surfaces can be performed in air with subnanometer resolution. In this design, scanning of the specimen in the x and y planes and surface profiling in z-axis are each monitored directly by capacitance sensors. The present SFM is capable of a resolutions of approximately 0.1 nm over 15 μm range in z-axis and about 1 nm over 50 pm scanning range in x− and y-axes with a repeatability of less than 1 nm. The linearity error was measured to be within the noise level. Specimens ranging from soft polymeric films to polished zerodur are used to illustrate its metrological capability.     

Friction and elasticity on a molecular scale

A molecular scale atomic force microscopy study of friction and elasticity is presented on a one-component lipid bilayer system - a model boundary lubricant. With a real area of contact on the order of the lattice spacings of the sample, the elastic compliances of single lipid molecules are recorded - the first report of a molecularly resolved elasticity map. The anisotropic and highly ordered structure of the lipid bilayer has been observed to cause contrast information in friction on molecularly flat areas, and to be dependent on the sliding direction. This anisotropic behavior of friction has been measured to be independent of normal elastic compliances. Only asymmetric indentation which causes in-plane compliances leads to heterogeneities in the elasticity map. In this fundamental study of friction, the effects of adhesion and elasticity are discussed.     

TectoRNA and 'kissing-loop' RNA: atomic force microscopy of self-assembling RNA structures

RNA molecules have been much less studied by atomic force microscopy (AFM) than have DNA molecules. In this paper, AFM imaging is presented for two different RNA molecules able to self‐assemble into complex supramolecular architectures. The first one is a molecular dimer of a 230‐nt RNA fragment coming from the RNA genome of a murine leukaemia virus. The monomeric RNA fragment, which appears by AFM as an elongated structure with a mean aspect ratio of 1.4, assembles into a dimer of elongated structures through the formation of a ‘kissing‐loop’ RNA interaction. The second one is a large supramolecular fibre formed of artificial self‐assembling RNA molecular units called tectoRNA. The fibre lengths by AFM suggest that there are 50–70 tectoRNA units per fibre. Some methods and limitations are presented for measuring molecular volumes from AFM images.     

High-resolution imaging of chromosome-related structures by atomic force microscopy

An atomic force microscope (AFM) was combined with a conventional optical microscope. The optical microscope proved to be very convenient for locating objects of interest. In addition, the high-resolution AFM image can be compared directly with the traditional optical image. The instrument was used to study chromosome structures. High-resolution chromosome images revealed details of the 30-nm chromatide structure, confirming earlier electron microscopic observations. Chromosomes treated with trypsin revealed a banding pattern in height which is very similar to the optical image observed after staining with Giemsa. Furthermore, it is shown that the AFM can be used to locate DNA probes on in situ hybridized chromosomes. Images of the synaptonemal complex isolated from rat spermatocytes revealed details that improve the understanding of the three-dimensional structure of this protein.     

采用计量型扫描力显微镜校准微纳米标准样板

为了建立质量保证体系,微米和纳米样板至今仍被广泛地应用于校准微纳米尺度的测量仪器中．介绍了应用由德国联邦物理研究所开发研究的、测量范围为25 mm×25 mm×5 mm的计量型扫描力显微镜(M-LRSFM)的校准方法．上述计量型扫描力显微镜配置有三个零拍的激光干涉仪,可分别测量沿x、y、z三条轴线方向的位移,因而其测量值可直接溯源于“米”定义．此种M-LRSFM能够校准横向的微纳尺度的结构尺寸,诸如阶梯高度、一维和二维光栅、镀层厚度、线宽、微纳尺度的表面粗糙度等．作为实例,介绍了一种横向样板的校准程序及获得的校准结果．研究表明这种方法适合于校验扫描电子显微镜(SEM)的放大倍率．     

荷能离子轰击固态材料形成孤立损伤的STM/SFM观测

在广阔的能区内（从ＭｅＶ到ＧｅＶ）系统地研究了荷能离子轰击固态材料形成孤立损伤的形态及其形成机理,分别利用具有原子分辨能力的扫描隧道显微镜／扫描力显微镜观测了离子轰击导电和绝缘材料产生孤立损伤（或离子潜径迹）的形态,大小,通过运用核能损和电子能损的理论对实验结果的分析,研究了离子轰击固态材料形成各种损伤的过程与机理。