Modal analysis of inter-area oscillations using the theory of normal modes

Based on the notion of normal modes in mechanical systems, a method is proposed for the analysis and characterization of oscillatory processes in power systems. The method is based on the property of invariance of modal subspaces and can be used to represent complex power system modal behavior by a set of decoupled, two-degree-of-freedom nonlinear oscillator equations.     

Microtubule-Targeting 7-Deazahypoxanthines Derived from Marine Alkaloid Rigidins: Exploration of the N3 and N9 Positions and Interaction with Multidrug-Resistance Proteins

Our laboratories have been investigating synthetic analogues of marine alkaloid rigidins that possess promising anticancer activities. These analogues, based on the 7-deazahypoxanthine skeleton, are available in one- or two-step synthetic sequences and exert cytotoxicity by disrupting microtubule dynamics in cancer cells. In the present work we extended the available structure–activity relationship (SAR) data to N3- and N9-substituted derivatives. Although N3 substitution results in loss of activity, the N9-substituted compounds retain nanomolar antiproliferative activities and the anti-tubulin mode of action of the original unsubstituted compounds. Furthermore, our results also demonstrate that multidrug-resistance (MDR) proteins do not confer resistance to both N9-unsubstituted and -substituted compounds. It was found that sublines overexpressing ABCG2, ABCC1, and ABCB1 proteins are as responsive to the rigidin analogues as their parental cell lines. Thus, the study reported herein provides further impetus to investigate the rigidin-inspired 7-deazahypoxanthines as promising anticancer agents.     

城市街道视域景观指数与邻里尺度特征效应

城市街道景观指数提取为城市街景研究量化途径之一。结合已有指数,提出用全景静态图的不同数据类型,分类计算视域景观指数的优化方法;提出基于计算机视觉尺度不变特征转换(SIFT)的关键点邻域尺度区间频数;采用层次聚类分析指数不同的邻里尺度最优簇数、贡献度,确定分布特征重要指数组成;探索不同指数作用于不同邻里尺度的特征效应。研究发现视域景观指数具有不同邻里尺度效应。研究指数中城市街道空间的绿视率和天空开阔度(空间组成层面)、关键点邻域尺度(0,10]和(10,20]区间频数(对象尺度层面),以及色彩丰富度指数(颜色层面)是构成城市街道分布特征的重要特征指数。通过确定不同邻里尺度城市街道特征分布,可以为城市街道空间的景观质量提升、量化管理和城市微更新提供参照。