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This paper explores suitable conditions for theimaging of DNA molecules by atomic force microscope (AFM). As a typical biological macro-molecule, DNA with geneticinformation has attracted extensive attention, which is an important research subject in biomedicine. In this work, 3-Aminopropyl Triethyl Silane (APTES), Ni2+and Mg2+ wereused to modify the surface of mica substrate, and DNAmolecules were adhered to the mica surface through the physical interaction of charges. The DNA molecules wereimaged using an AFM under both air conditions and liquid conditions. By analyzing the images of DNA molecules obtainedin the experiments, it was found that the mica surface modifiedwith Ni2+had the best imaging quality under the liquidcondition. This work will be useful for the study of high quality AFM imaging of DNA molecules, and the manipulation of DNAmolecules by AFM mechanical forces.

This paper presents a method for the stretching of DNAmolecules on mica surfaces by magnetic field. In the experiment, themagnetic fields with different intensities were generated using a selfmade cylindrical coil and were used to study their effects on DNAmolecules. The magnetic field intensity was controlled by theelectric current flowing through the coil. The imaging of DNAmolecules was performed by atomic force microscope (AFM) in thesame position on the mica surface after the treatment with themagnetic field. It was found that the DNA molecules were graduallystraightened with the increase of magnetic field intensity, and thestraightening performance was better than that of the molecularcombing method. In addition, the degree of DNA straightening was related to the speed at which DNA molecules were dropped to themica surface, the amount of DNA charges and the direction ofmagnetic field.

This paper presents a method forthe manipulationofmagnetic nanoparticles byoptically induced dielectrophoresis (ODEP) device that can realize the transportation andconvergence of nanoparticles. ODEP can be realized with a sandwich structure of three layers including the photoconductive layer, the liquid layer with the sample and the indium tin oxide electrode (ITO) layer. In this work, magneticnanoparticles with the diameter of 10-100nm were successfullymanipulated by positive dielectrophoresis force. The solutionwith magnetic nanoparticles on a mica substrateplaced in thesandwich structurewas dried in the air and imaged by atomic force microscope (AFM) The AFM images showed that themagnetic nanoparticles were converged in the illumination area.This method can be used to manipulate magnetic nanoparticles.

The Wenchuan Ms 8.0 earthquake on May 12, 2008 induced a huge number of landslides. The distribution and volume of the landslides are very important for assessing risks and understanding the landslide — debris flow — barrier lake — bursts flood disaster chain. The number and the area of landslides in a wide region can be easily obtained by remote sensing technique, while the volume is relatively difficult to obtain because it requires some detailed geometric information of slope failure surface and sub-surface. Different empirical models for estimating landslide volume were discussed based on the data of 107 landslides in the earthquake-stricken area. The volume data of these landslides were collected by field survey. Their areas were obtained by interpreting remote sensing images while their apparent friction coefficients and height were extracted from the images unifying DEM (digital elevation model). By analyzing the relationships between the volume and the area, apparent friction coefficients, and the height, two models were established, one for the adaptation of a magnitude scale landslide events in a wide range of region, another for the adaptation in a small scope. The correlation coefficients (R2) are 0.7977 and 0.8913, respectively. The results estimated by the two models agree well with the measurement data.