A robust solution for PI-based LFC problem with communication delays

This paper addresses a new method to design a PI-based load-frequency control (LFC) with communication delays. First the LFC problem is reduced to a static output feedback control synthesis for a multiple delays system, and then the control parameters are easily carried out using robust H∞ control technique. A 3-control area power system example is given to illustrate the proposed control methodology and the results are compared with the delay-less system-based H∞ control design

Cytotoxic cardenolide and sterols from Calotropis gigantea

The dichloromethane extract from the leaves of Calotropis gigantea Linn. was strongly cytotoxic against non-small cell lung carcinoma (A549), colon carcinoma (HCT 116) and hepatocellular carcinoma (Hep G2), and non toxic to Chinese hamster ovary (AA8). The extract afforded uscharin (1), 3,5,8-trihydroxy-24-methylcholest-6,22-diene (2), a mixture of (24R)-3β-hydroxy-24-ethylcholest-5-en-7-one (3a) and 6β-hydroxy-24- ethylcholest-4,22-dien-3-one (3b), and another mixture of (24R)-24-ethylcholest- 4-en-3-one (4a) and (24S)-24-ethylcholest-4,22-dien-3-one (4b). Cardenolide 1 exhibited extreme toxicity to A549, HCT 116 and Hep G2 with IC50 values of 0.003 μg/mL, 0.013 μg/mL, and 0.018 μg/mL, respectively, while sample 3 exhibited an IC50 of 1.35 μg/mL, 4.46 μg/mL, and 3.83 ́g/mL, respectively