Measuring radial Young’s modulus of DNA by tapping mode AFM

Based on tapping mode AFM imaging, a method was demonstrated to evaluate compression elasticity of single double-stranded DNA （dsDNA） molecules in the force region. With images under ambient conditions, Young＇s moduli of dsDNA in compression were calculated. Results demonstrated that Young＇s moduli of dsDNA can be simply deduced according to the proposed model. The method can also be used to evaluate the compression elasticity of similar soft nanomaterials.     

使用碳纳米管AFM针尖的蛋白质高分辨率成像

原子力显微镜(AFM)是分析生物分子结构的有效手段,而目前使用的探针针尖的性质限制了高分辨率图像的获得。该文将碳纳米管安装到原子力显微镜的传统针尖上,制作出碳纳米管针尖以解决这个问题。运用碳纳米管针尖在大气常温条件下获得了由3个单元组成的小鼠抗体IgG蛋白质的Y形结构,并且分子的尺寸与X射线晶体衍射的结果非常接近,这种效果用传统针尖是无法获得的。获得的蛋白质分子超微结构的高分辨率图像为研究蛋白质分子功能提供了有价值的信息。     

施扰建筑高度对主建筑层升力影响的试验研究

利用刚性模型测压试验,研究了施扰建筑相对高度变化对主建筑层升力系数和层脉动升力功率谱的影响规律.试验包含了3个并列位置、5个串列位置和3个斜列位置.结果表明:建筑物并列时,高度比越大则层平均升力系数大,层脉动升力功率谱受影响的范围大;建筑物串列时,高度比对层平均升力系数的影响很小,对层脉动升力系数的大小及沿高分布形式有显著影响,施扰建筑高度超过受扰建筑时层脉动升力功率谱受到的影响很大,尤其是顶部区域;斜列工况时,并列间距比对影响规律起主导作用.     

原子力显微镜相位象的理论和应用

文章讨论了原子力显微镜在轻敲模式下相位象的两类主要理论,简谐近似理论和能量理论;介绍了相位象在软材料如聚合物等表面分析研究上的应用,以及目前相位象研究的新问题。     

粉体样品制样方式对AFM图像的影响

研究不同的粉体样品制样方式对AFM图像的影响,实验证明磨具压片使松散的样品紧密而更有利于扫描,使用轻敲模式,设置点小于1V,获得清晰图片。     

基于滑模控制的空气悬架车高控制系统研究

以提高空气悬架车高控制精度为目的,充分考虑空气悬架系统充放气过程的非线性特性,建立了气体管路流量特性方程,并结合变质量气体热力学定律,建立电磁阀开启和关闭时的空气弹簧充放气压力梯度方程,实现空气弹簧充放气过程的非线性特性数学描述,并进一步完成空气悬架车高升降的1/4车模型. 针对充放气过程的非线性特性,基于微分几何理论,将车高升降模型通过状态反馈进行全局线性化,在线性域中设计滑模控制器,进而经过线性逆变换,得到原坐标系中的非线性车高控制算法. 仿真试验表明,基于状态反馈线性化方法设计的滑模控制器,能够有效克服充放气过程的非线性特性,消除过充过放现象,显著提高车高控制品质和精度.      

Mapping CD20 molecules on the lymphoma cell surface using atomic force microscopy

Atomic force microscopy (AFM) was used to locate CD20 molecules on the surface of lymphoma Raji cells. Rituximab (a monoclonal antibody against CD20) molecules were linked onto the AFM tip via a polyethylene glycol (PEG) linker. Raji cells were adsorbed onto glass slides coated with poly-L-lysine. First, the CD20 distribution in a local area of the cell surface was visualized using the AFM lift scan mode. Second, 16 × 16 force curves were obtained from the same cell area to construct the CD20-rituximab binding force map. Finally, free rituximab was added to block the CD20 molecules on the cell surface and the lift phase image and CD20-rituximab force map were obtained again. The experimental results indicated that when the lift height was greater than the length of the PEG linker, no recognition sites were observed in the lift phase image. However, as the lift height decreased to the length of the PEG linker, some recognition sites were observed in the lift phase image and these sites were generally consistent with the pixels in the force map. After blocking, both the recognition sites in the lift phase image and the gray pixels in the binding force map decreased markedly. These results can improve our understanding of the distribution of protein molecules on the cell surface and facilitate further investigations into cellular functions.     

黄原胶分子形貌的原子力显微镜研究

通过溶胶凝胶的方法制备了黄原胶水溶液,并采用轻敲模式原子力显微镜(AFM)对不同浓度的黄原胶分子溶液的表面微观结构形态进行了观察.实验结果表明,轻敲模式下的AFM能够观测到黄原胶分子的微观结构,浓度为0.1g/L时分子类似于球状体的颗粒,以多聚体形式存在.浓度达到0.01g/L时能够形成稳定的网状结构,当浓度达到0.001g/L的情况下形成单个纤维分子.利用AFM截面软件对网状结构和单个纤维进行分析,发现了云母表面出现的黄原胶分子分别为双链和单链.本文中提出了黄原胶分子从网状结构到单个纤维形成过程的假设模型,很好地解释了实验观察结果,对以后的实验研究有很大意义.     

敲击模式扫描近场光学显微镜

为了实现敲击模式的扫描近场光学显微镜 ,采用以石英音叉为灵敏探测器件 ,将光纤探针垂直音叉侧臂粘接 ,使探针在垂直样品的方向上振动 ,以“敲击”方式探测样品表面的信息 ,实现近场范围的高度控制。仪器结构紧凑 ,操作方便 ,灵敏度高 ,可用于液体环境下的样品探测 ,在对样品形貌进行探测的同时可实现对光信号的调制。将这种探测模式应用于实验 ,获得 2 40 0线 /mm光栅、光盘母盘和生物细胞的形貌图像。实验证明 :这种探测方式分辨率优于 2 0 0 nm,适用于不同硬度的样品 ,可以作为材料学、生物学等领域的有力工具。     

间歇模原子力显微镜扫描探针的受迫振动解

提出了一个间隙模原子力显微镜全动态工作的模型 ,用参数变换和模式展开方法 ,得到了具有粘滞阻尼和分段线性相互作用力的扫描探针的受迫弯曲振动微分方程的分析解 ,间歇模原子力显微镜扫描探针的受迫振动解 ,由接触模解和非接触模解交替工作而构成     

Combined-dynamic mode “dip-pen” nanolithography and physically nanopatterning along single DNA molecules

Atomic force micriscope (AFM)-based dip-pen nanolithography (DPN) is an emerging approach for constructing nanostructures on material surfaces such as gold, silicon and silicon oxide. Although DPN is a powerful technique, it has not shown its ability of direct-writing and patterning of nanostructures on surfaces of soft materials, for example biomacromolecules. Direct depositing on soft surfaces becomes possible with the introduction of a combined-dynamic mode DPN rather than mostly used contact mode DPN or tapping mode DPN. In this report, the combined dynamic mode DPN is used for direct depositing protein ink on DNA molecules at the nanometer scale.     

间歇模原子力显微镜扫描探针的非线性振动

提出了一个用于描述间歇模原子力显微镜扫描探针全动态工作的非线性受迫弯曲振动模型，这个模型考虑了一个附加于扫描探针上的质量和任意类型的探针－样品表面间的非线性相互作用力。用参数变换和模式展开方法求得了间歇模原子力显微镜扫描探针非线性受迫弯曲振动的解，给出了数值模拟的结果。     

基于二氧化碳红外热成像的火焰起升高度分析

基于CO_2红外热成像方法拍摄了可控活化热氛围下的正庚烷液滴群预混射流火焰,测量了火焰起升高度,研究了热氛围协流温度、液滴群预混当量比、液滴群射流速度3个因素对起升高度的影响规律.结果表明:射流火焰起升高度主要受到化学着火延迟期控制,起升高度随着协流温度的升高而降低,但当协流温度足够高时,起升高度几乎不再变化;当量比增大会使物理着火延迟期缩短,从而使火焰起升高度降低;在相同的当量比下,如果协流温度较低,射流出口速度增加会提高火焰起升高度,而当协流温度高于某临界温度后,加大射流出口速度却会降低火焰起升高度.     

提水灌区多级泵站站址高程的确定

文章从系统的观点出发，提出了一种实用的确定提水灌区多级泵站站址高程的方法．     

Research on the reconstruction of fast and accurate AFM probe model

The AFM image will be distorted due to the tip-broadening effect. It may be mathematically represented as the effect of the tip’s convolution on the real image. As a result, the true geometry of the sample surface can not be obtained. If the tip shape could be known accurately, such distortion can be eliminated with the adoption of disconvolution operation. It is of practical significance in the accurate reconstruction of the AFM image. Among the current tip modeling algorithms, the blind tip estimation algorithm based on mathematical morphology is widely applied. However, it takes much time and has difficulties in defining the optimal noise threshold. In view of the above problems, this paper proposes a new blind tip evaluation method to accelerate the speed of blind tip modeling calculation and realize the accurate reconstruction of the AFM image. The simulation and the experimental results demonstrate the feasibility and effectiveness of the above research method.     

The experimental rules of mica as a reference sample of AFM/FFM measurement

For the friction measurements with AFM/FFM, usually the relative values of friction signal can be obtained. In order to compare the micro-tribological properties of different samples, mica is often used as an reference sample for friction measurement. However, due to the friction force of new cleaved mica surface is unstable, it is urged to systematically investigate the tribological properties of mica to design the experimental rules of the reference sample mica for friction measurements. Experimental results show that the friction of mica varies with the cleaving time, humidity and surface state of tip. The friction measured with different tips on mica varies in the range of ± 15%. For a new tip, the friction increases with the tip’s wear and then becomes stable. For new cleaved mica, the friction increases within the first two hours and then keeps unchanged. The friction of mica also decreases with the relative humidity because of its hydrophilicity.     

大产液量水平气井不同气举方式气液两相流研究

连续气举是产水量大的水平气井重要排采措施,针对现场正举和反举的特点,为揭示气田开发过程中反举条件下油管和正举条件下油套环空内的气液两相流流动规律,分别用水和空气在套管内径为127.3mm、油管外径为73mm的油套环空和内径为60mm的油管内进行了井筒气液两相管流模拟实验,对低压积液气井气举时井筒流动规律进行了研究分析,分析了井筒中气相和液相的体积流量、注气方式等因素对井筒压降和持液率的影响。实验结果表明,在相同气、液流量条件下,反举时的持液率比正举持液率小;不同气举方式下的井筒压降随注气量的增加呈不同的变化趋势,反举时的井筒压降比同工况下正举的压降大,对于产液量较大且有一定地层能量的气井,推荐采用反举方式进行气井排水采气。     

Application of atomic force microscopy to living samples from cells to fresh tissues

Atomic force microscopy is a novel method for imaging and characterization in biomedicine. However, high-resolution imaging of living samples from cells to tissues still remains a challenge. In this paper, two types of AFM working mode （contact mode and tapping mode） which are utilized for the imaging of living cells and tissues are discussed. A new magnetic tapping mode （MAC mode）, which is more suitable for living samples, and a novel data collecting system named TREC, are also introduced.     

木质框架土壤渗滤系统中氨氮沿程变化的半经验公式

为解决木质框架土壤渗滤系统(WFSI)在处理干清粪养猪废水时的设计高度问题,构建了高度为1.2 m的WFSI反应器。在表面水力负荷为0.08,0.2和0.32 m3·(m2·d)-1,氨氮负荷为27.3±6.0,88.5±9.4,122.7±7.4,28.1±3.7,114.9±10.3 g·(m3·d)-1等条件下运行了WFSI反应器,并根据扩散理论和水流在反应器的流态推出了氨氮浓度与滤层高度间的函数关系式。通过对沿程土壤层中的含水率和氨氮浓度的测量和函数拟合,得到了含水量沿程变化和氨氮浓度沿程变化的经验公式。利用经验公式对氨氮浓度与滤层高度间的函数关系式进行求解,并得到了系统构造常数。通过对比五种运行条件得到的系统构造常数,验证了本研究得到的氨氮浓度与滤层高度间的函数关系是较为可信的。