基于树枝状聚合物的无机纳米颗粒的制备及应用

树枝状聚合物具有一些独特性质,包括规整且高度支化的三维结构、完美单分散尺寸、内部空腔以及表面大量的官能团等,因而其在催化、检测、生物医用领域具有潜在应用。这些应用的改进或者实现,往往需要在树枝状聚合物中引入无机纳米颗粒,从而制备得到基于树枝状聚合物的无机纳米颗粒。另一方面,树枝状聚合物的存在能够提升无机纳米颗粒在溶液中的稳定性、抑制团聚,从而长时间保留纳米颗粒的优异性能。在过去几十年,因为其优异的性质和潜在的应用,基于树枝状聚合物的无机纳米颗粒吸引了众多科研人员的关注。依据其结构特点,可以将基于树枝状聚合物的无机纳米颗粒大致分为以下三类:(1)树枝状聚合物包裹的无机纳米颗粒;(2)树枝状聚合物稳定的无机纳米颗粒;(3)树枝化基元稳定的无机纳米颗粒。本文侧重归纳并总结近五年基于树枝状聚合物的无机纳米颗粒的制备方法,以及其在催化、生物医用、检测领域的研究进展,并对其制备方法和应用发展进行了展望。

Contact parameter analysis and calibration in discrete element simulation of rice straw

Discrete element method was used to study and analyze the interaction between rice straws and between rice straw and agricultural machinery parts,thereby providing a scientific basis for post-harvest paddy field processing.Calibrations of rice straw-rice straw,rice straw-agricultural machinery part contact parameters(collision recovery coefficient,static friction coefficient and rolling friction coefficient)constitute an important prerequisite for the discrete element research process.In this study,the collision recovery coefficients of rice straw-steel and rice straw-rice straw were 0.230 and 0.357,respectively,which were calibrated by the collision method.The static friction coefficient and rolling friction coefficient of rice straw-steel were 0.363 and 0.208 respectively,which were calibrated by the inclined plate method and the slope method.The static friction coefficient and rolling friction coefficient of rice straw-rice straw were 0.44 and 0.07,respectively,which were calibrated by the split cylinder method.The paired t-test showed insignificant differences between calibration parameter simulation results and the physical test values(p>0.05).Taking the angle of repose that reflecting rice straw flow and friction characteristics as the evaluation index,the verification tests of the above calibration values indicated that the simulated angle of repose has no significant difference from the physical test value(p>0.05).The side plate lifting test on rice straw of different lengths showed no significant difference between the simulated angle of repose and the physical test value(p>0.05).This study can provide a basis for contact parameters choice in discrete element simulation analysis with rice straw-rice straw and rice straw-agricultural machinery parts as the research object.The calibration method can provide a reference for the contact parameter calibration of other crop straws.

Microfluidic methods for cell separation and subsequent analysis

Cell is the most basic unit of the morphological structure and life activity of an organism. Learning the composition, structure and function of cells, exploring the life activities of cells and studying the interaction between cells are of great significance for human cognition and control of the life activities of organisms. Therefore, rapid, convenient, inexpensive, high-precision and reliable methods of cell separation and analysis are being developed to obtain accurate information for the study of cytology and pathology.Microfluidic chip is a new emerging technology in recent years. It has a micromanufacturing structure,which can not only realize the precise space-time control of fluid and cells, but also reproduces the threedimensional dynamic microenvironment of cell growth in the body. In addition, the microfluidic chip has unique microphysical properties and facilitates the integration of microdevices, which provides the possibility of real-time monitoring, continuous culture, separation and enrichment, and even in situ analysis of cells. In this review, we summarized recent advances in the development of different techniques for cell isolation and analysis on microfluidic platforms. Focus was put on biochemical and physical methods for cell separation on microfluidic chips. Subsequent cell analysis depending on fluorescence, Raman, cytomicroscopic imaging, mass spectrometry and electrochemical methods also was remarked. Through analyzing and learning the advantages and disadvantages of different technologies, we hope that microfluidic chips will continue to be improved and expanded for medical and clinical applications.