基于AFM成像的DNA长度的计算机统计处理

利用计算机图像处理技术 ,对自然沉积DNA和拉直DNA分子AFM图像的长度进行了自动统计测量 ,并与DNA分子的理论长度进行了比较。该方法在DNA分子的AFM图像的基础上 ,将DNA分子拟合成曲线 ,用插值法求得DNA分子长度 ,整个过程实现了自动化。结果表明 ,该方法测得自然沉积的某DNA分子长度为 (180 .4± 16.4 )nm ,与理论长度 185 .0nm相当符合。该方法与拉直法和直接法求DNA分子长度相比是一次改进 ,也为其它基于AFM图像的线状物体求长度提供了一种新的测量方法。对另一组拉直DNA测量的结果表明 :拉直后DNA分子长度为 (34 3.6± 2 0 .7)nm ,与理论长度 30 7.0nm相比明显变长 ,这表明对自然沉积DNA进行长度测量的必要性 ,保证了DNA分子的长度不受拉直后有所伸长的影响。     

DNA分子及其双链断裂碎片的AFM观测

生物大分子DNA是生命信息的载体,是辐射生物学效应最重要的靶分子。为了进一步研究辐射致DNA损伤的机理,首先需要掌握观测DNA分子及其双链断裂(Double Strand Breaks,DSB)碎片的技术。在大气状态下,使用先进的原子力显微镜(AFM)技术获得了3种经过提纯的DNA分子的直观图像;在水溶液中,利用~(241)Am-α源辐照装置对其中一种DNA分子进行了低剂量照射,利用AFM     

云母-石墨烯界面纳米尺度受限水层的湿润-去湿润研究

研究受限于纳米尺度空间的水或者其他分子液体的性质在生物学、材料科学、摩擦学、微流控等领域有重要的意义。但直接通过显微镜观察界面上的纳米尺度液体的润湿动态过程仍然是个挑战。近年来受益于石墨烯等二维晶体材料的发现与发展,由石墨烯作为覆盖材料形成的受限体系为这一问题提供了很好的解决方式。通过原子力显微镜原位成像发现,由石墨烯与云母组成的受限体系中包含水层,一层水层的高度约为0.37 nm,而通过改变周围空气的湿度可以调控受限体系中水层的湿润-去湿润可逆性变化。同时实验中观察到了水层随湿度变化时呈现出的不同的生长方式。平整的石墨烯覆盖层提供了一种新的尺寸可调整的纳米通道,可对纳米尺度的受限水层实现高分辨成像,为纳米流体器件的发展提供了可能性。     

非接触调频模式AFM的发展及生物学应用

非接触调频模式原子力显微镜(AFM)可实现高分辨成像,其探针针尖与样品间的相互作用力非常小,能最大限度减少样品形变。本文综述非接触调频模式原子力显微镜在真空和溶液中的高分辨成像发展,并以DPPC磷脂双分子层和人类免疫球蛋白IgM为例,介绍了该系统在生物结构学研究中的应用。     

微管在APS-云母上的固定和AFM成象

借鉴原子力显微镜和相关显微镜的微客研究的制样方法,应用－三乙氧基硅烷－云母作为微管的ＡＦＭ成象和性质研究的衬底,获得了满意的结果。本方法对进一步研究微管的性质和动力学研究非常重要。     

AuNPs@MPA-PEG纳米粒子对肿瘤细胞辐射敏感性影响

为研究3-巯基丙酸(MPA)-聚乙二醇(PEG)修饰的金纳米粒子(AuNPs@MPA-PEG)对人宫颈癌Hela细胞辐射敏感性的影响,以柠檬酸钠为稳定剂,硼氢化钠为还原剂,还原氯金酸制备5.4 nm的金纳米粒子(AuNPs),并分别用MPA-PEG、PEG修饰金纳米粒子,制备AuNPs@MPA-PEG、AuNPs@PEG。通过电感耦合等离子体发射光谱仪检测Hela细胞及细胞核对AuNPs、AuNPs@MPA-PEG、AuNPs@PEG的吸收量;克隆形成法测定AuNPs、AuNPs@MPA-PEG、AuNPs@PEG对X射线照射后Hela细胞存活率的影响。结果表明,Hela细胞和细胞核对AuNPs、AuNPs@MPA-PEG、AuNPs@PEG的吸收量具有浓度依赖性。MPA-PEG、PEG修饰减少细胞对金纳米粒子的吸收,但是MPA-PEG对金纳米粒子进行修饰,却增加细胞核对金纳米粒子的吸收。对于160 kVp X射线,AuNPs、AuNPs@MPA-PEG、AuNPs@PEG均对Hela细胞有辐射增敏作用,但增敏效果不明显。MPA-PEG、PEG修饰没有增加金纳米粒子的辐射增敏作用。     

哑铃状纳米金的合成及其光吸收效应的研究

通过在DNA组装的纳米金棒上实现金的再生长,我们合成了一种哑铃状的复合金纳米结构。通过紫外-可见吸收发现,该结构在较小的尺寸下,表现出良好的近红外吸收特性,这为进行深层组织光热治疗提供了一种良好的载体。另外,通过改变还原剂与氯金酸的比率及还原剂的种类,可以得到金棒两端生长"刺状突起"和"海胆状"金纳米结构。由于这两种结构具有较大的比表面使其在表面增强拉曼和金属催化等方面具有潜在的应用;同时该结构可用于包裹标记同位素作为放射性药物进入细胞或体内的载体。     

Damage of DNA ends induced by mechanical force during AFM nano-manipulation

An experimental and statistical study was carried out to explore the effects of mechanical forces on the ends of linear double-stranded DNA (dsDNA) fragments. Mechanical force was applied onto individual DNA molecules during atomic force microscope (AFM)-based picking-up manipulation. By comparing the PCR efficiency of two DNA fragments with primers either at ends or at the inner regions, it was found that the ends of DNA fragments were damaged during picking-up process.     

水和乙醇对DNA分子二维操纵的机制研究

DNA分子具有稳定的物理化学性质,成为纳米领域的重要实验材料,已有许多将其作为模板构建纳米线等方面的研究,因而,DNA分子的操纵技术显得尤为重要.分子梳技术利用水流动时的弯月面操纵DNA分子,是构建特定的DNA分子纳米结构的一个重要方法.本文采用一种改良分子梳技术,用原子力显微镜观察水和乙醇操纵DNA分子后形成的规则图案,分析弯月面和液流对DNA分子的作用,并讨论了液体和DNA分子在操纵时的作用机制.     

纳米金在肿瘤检测及放射治疗中的应用

简述纳米金探针的组装和检测原理,总结了纳米金探针在肿瘤细胞检测、医学成像和放射治疗中的应用进展,并对其在今后的应用发展前景进行了展望。     

Cold fusion reaction products and their measurement

The major reaction products that have been possibly associated with cold fusion reactions are neutrons, protons, tritium, He-3, He-4, internal conversion electrons, and gamma radiation. The branching ratios and relative reaction rates for these products are examined for consistency with cold fusion experiments. Both theoretical calculations and experimental data are examined and presented. The He-4 plus internal conversion reaction has been proposed to explain the absence of neutrons or gamma rays in successful cold fusion experiments. However, this reaction is not favored, even in a deuterium-palladium system. Measurement of these reactions must be made carefully owing to the presence in the background of 2.2-MeV gamma rays, background tritium in heavy water, and neutrons from the photodisintegration of the deuterium from background radiation. These problems confronting cold fusion experiments are addressed.     

Purification of uranium products in crystallization system for nuclear fuel reprocessing

Uranium crystallization system has been developed to establish an advanced aqueous reprocessing for fast breeder reactor (FBR) fuel cycle. In the crystallization system, most part of uranium in dissolved solution of spent FBR-MOX fuels is separated as uranyl nitrate hexahydrate (UNH) crystals by a cooling operation. The targets of U yield and decontamination factor (DF) on the crystallization system are decided from FBR cycle performance and plutonium enrichment management. The DF is lowered by involving liquid and solid impurities on and in the UNH crystals during crystallization. In order to achieve the DF performance (more than 100), we discuss the purification technology of UNH crystals using a Kureha Crystal Purifier (KCP). Results show that more than 90% of uranium in the feed crystals could be recovered as the purified crystals in all test conditions, and the DFs of solid and liquid impurities on the purified UNH crystals are more than 100 under longer residence time of crystals in the column of KCP device. The purification mechanism is mainly due to the repetition of sweating and recrystallization in the column under controlled temperature.     

氦离子辐照非晶态合金的表面损伤研究

用扫描电子显微镜研究了室温下氦离子辐照Fe77Ni5B18等 10种非晶态合金的表面形貌。氦离子的能量为 4 0keV和 6 0keV ,总注量为 1.0× 10 18— 4 .0× 10 18He/cm2 。对于不同的注量和不同的材料 ,观察到了层离、发泡、剥落、发泡破裂、二代发泡和多孔结构等多种表面损伤类型。测量了泡的直径和剥落泡皮的厚度 ,并讨论了表面损伤类型和初现的临界注量与材料种类和离子能量的关系。     

Determination of absorbed doses in organisms exposed to emanations and their daughter products

Earlier, we considered the problem of absorbed doses created by short-lived a emitters in inhaling radon [3]. The present paper describes certain methods for determining absorbed doses due to radon itself, short-lived RaB and RaC ß-emitters, and long-lived elements of the radon family. Similar calculations were performed for the thoron and actinon families, as a results of which new values for the maximum allowable concentration of thoron and actinon in air are recommended. The proposed method for determining absorbed doses can be used in the case where elements of any radioactive chain have penetrated the organism. It is demonstrated that personnel health monitoring with respect to the radiation of emanation daughter products that have settled in the respiratory system is a problem which can be solved in a practical manner.The author extends his thanks to Yu. M. Shtukkenberg, N. G. Gusev, and O. I. Leipunskii for their discussion of the paper and valuable remarks.     

Influencing factors on local reduction of graphene oxide with a heated AFM tip

In this paper,the factors influencing the local thermal reduction of graphene oxide (GO) sheets are investigated.The lateral force microscopy and scanning polarization force microscopy verify that the heated tips of atomic force microscope (AFM) can thermally reduce the GO into electrical conductive nanostructures.The tip temperature,heating time,and loading force applied by the AFM tip are found to have important effects on the thermal reduction of GO,while the environmental humidity is negligible.     

The effect of internal conversion of nuclear fission products on their degree of ionization

The charge-state distribution of ²⁴¹ Pu-fission products (A = 131–145) was measured at kinetic energies of E_k = 67, 70 and 73 MeV. Smearing of the fine structure and separation of atomic and nuclear ionization effects of fission products was achieved by again changing their charge t < 5 × 10⁻¹⁰s after the fission event. The contribution of nuclear ionization effect has been shown to depend on excitation energy and on the structure of the nuclei. For some masses this contribution reaches 50%.     

Structural characterization of Fe/Ag bilayers by RBS and AFM

Fe/Ag thin films are intensively investigated due to their special magnetic properties. Recently a deposition-order dependent asymmetric interface has been found. When iron is grown on silver, the interface is sharp, while the growth of Ag on Fe results in a long, low-energy tail of the Ag peak in the Rutherford backscattering spectrometry (RBS) spectra. The main purpose of this paper is to show that the low-energy Ag tail is caused by grain boundary diffusion, and that, when elevating the growing temperature of the Ag layer this effect becomes more significant. Two sets of polycrystalline and epitaxial Fe/Ag bilayers were prepared simultaneously onto Si(1 1 1) and MgO(1 0 0), respectively. The iron layers were grown at 250 °C and annealed at 450 °C in both sets, while the Ag layer was grown in the first set at room temperature (RT) and in the second set at 250 °C (HT). The sample composition, the interface sharpness and the quality of the epitaxy were studied by Rutherford backscattering spectrometry (RBS) combined with channeling effect. The surface morphology was determined by atomic force microscopy (AFM). RBS spectra show that in the case of RT samples the epitaxial MgO/Fe/Ag bilayer has sharp, well-defined interface, while for the polycrystalline Si/Fe/Ag sample the silver peak has a low-energy tail. Both the Fe and Ag peaks smeared out in the case of HT samples. AFM-images show that the RT samples have a continuous Ag layer, while the HT samples have fragmented surfaces. The RBS spectra taken on the HT samples were successfully simulated by the RBS-MAST code taking into account their fragmented structures.     

Investigation of surface microgeometry and the active nucleation cavities using AFM

Boiling surface measurements have been conducted to identify vapor/gas trapping cavities by using atomic force microscopy (AFM) and scanning electron microscope (SEM) techniques. Three specimens with different surface treatments were tested. The measurement results obtained in this study confirm the existence of two types of cavities, pit type and groove type, which are able to entrap vapor/gas for most commonly used liquids. Based on AFM, a more accurate estimation of cavity radius and cone angle distribution function will become accessible.