Nanoscopic surface patterns of diblock copolymer thin films

The surface topography of thin diblock copolymer films is studied by atomic force microscopy (AFM). With AFM an island-to-ribbon transition is observed for symmetric polystyrene-b-poly (4-vinylpyridine) (PS-b-P4VP) on mica with increasing solution concentration. Our study also demonstrates how the formation of the pattern strongly depends on the copolymer composition based on the volume fraction. The substrate and solvent used both have great effects on the morphology of the thin films. Only by using highly polar substrate (mica), can we gain regular pattern. The reason why the regular islands cannot be obtained with symmetric PS-b-P4VP on graphite is also explained. On mica using nonselective and selective solvents, a rather regular pattern can be obtained. The difference is only in the solution concentration for forming regular patterns

The complete chloroplast genome sequence of Oxalis corniculata (L.)

Oxalis corniculata L. is a perennial herb with a world-wide distribution. In this study, we sequenced the complete chloroplast genome of O. corniculata, which exhibited a circular genome of 155,182 bp in length with 37.5% GC content. The chloroplast genome contained a canonical quadripartite structure with a large single copy (LSC) region of 83,936 bp, a small single copy (SSC) region of 17,048 bp and a pair of 25,581 bp inverted repeats (IRs). A total of 108 unique genes, including 76 protein-coding genes (PCGs), 28 tRNA genes and four rRNA genes were found in this chloroplast genome. The phylogenetic tree was constructed based on O. corniculata and other 11 chloroplast genome sequences, which showed that O. corniculata was closely grouped with of O. corymbosa and O. drummondii

Numerical Simulation Investigation on Parameter Optimization of Deep-Sea Mining Vehicles

Abstract The four-track walking mining vehicle can better cope with the complex terrain of cobalt-rich crusts on the seabed. To explore the influence of different parameters on the obstacle-crossing ability of mining vehicles, this paper took a certain type of mine vehicle as an example and establish a mechanical model of the mine vehicle. Through this model, the vehicle’s traction coefficient variation could be analyzed during the obstacle-crossing process. It also reflected the relationship between the obstacle-crossing ability and the required traction coefficient. Many parameters were used for this analysis including the radius of the guide wheel radius, ground clearance of the driving wheel, the dip angle of the approaching angular and the position of centroid. The result showed that the ability to cross the obstacles requires adhesion coefficient as support. When the ratio between obstacle height and ground clearance of the guide wheel was greater than 0.7, the required adhesion coefficient increased sharply. The ability to cross obstacles will decrease, if the radius of the guide wheel increases, the height of the driving wheel increases or the dip angle of the approaching angular increases. It was most beneficial to cross the obstacle when the ratio of the distance between the center of mass and the front driving wheel to the wheelbase is between 0.45‒0.48. The results of this paper could provide reference for structural parameter design and performance research for mining vehicles