Static deflection measurements of cantilever arrays reveal polymer film expansion and contraction

An optical static method of detection is used to interpret surface stress induced bending related to cantilevers coated on one side with poly(vinyl alcohol), poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate), and poly(vinyl chloride-co-vinyl acetate-co-2-hydroxypropyl acrylate), or respectively, PVA, PVB, and PVC, and exposed to various solvent vapors. Results indicate that the adsorption and surface interactions of the different solvent vapors that cause polymer swelling and shrinking lead to rearrangements, which have been shown to change the elastic properties of the polymer film, and subsequently, the spring constant of the polymer coated cantilever. Static deflection measurements allow the direction of cantilever bending to be determined, which adds a new dimension of usefulness for surface functionalized cantilevers as transducers in the development of novel microelectromechanical systems (MEMS).     

Experimental verification of rapid, sporadic particle motions by direct imaging of glassy colloidal systems

We analyze data from confocal microscopy experiments of a colloidal suspension to validate predictions of rapid sporadic events responsible for structural relaxation in a glassy sample. The trajectories of several thousand colloidal particles are analyzed, confirming the existence of such rapid events responsible for the structural relaxation of significant regions of the sample, and complementing prior observations of dynamical heterogeneity. Thus, our results provide the first direct experimental verification of the emergence of relatively compact clusters of mobility which allow the dynamics to transition between the large periods of local confinement within its potential energy surface, in good agreement with the picture envisioned long ago by Adam and Gibbs and Goldstein.     

高分离度快速液相色谱法测定牛黄解毒片中黄芩苷的含量

采用高分离度快速液相色谱(RRLC)测定牛黄解毒片中黄芩苷的含量。色谱柱为Zorbax XDB-C18(4.6×50mm,1.8μm),流动相为甲醇-水-磷酸(45∶55∶0.2),检测波长315nm,流速0.5mL.min-1,柱温为30℃。黄芩苷在0.15—1.35μg(r=0.9999)范围内峰面积与浓度呈良好的线性关系,加样回收率为100.41%,RSD=1.42%。采用高分离度快速液相色谱(RRLC)测定复方牛黄解毒片中黄芩苷的含量,缩短了保留时间,提高了效率,降低了成本。本方法简便、准确,结果稳定。