Aloe vera continues to be used for wound healing as a folk medicine. We previously reported that A. vera gel has angiogenic activity. In this study, we report upon the isolation of an angiogenic component beta-sitosterol from A. vera and examination of its effect upon damaged blood vessels of the Mongolian gerbil. In a chick embryo chorioallantoic membrane assay, beta-sitosterol was found to have an angiogenic effect. It enhanced new vessel formation in gerbil brains damaged by ischaemia/reperfusion, especially in the cingulated cortex and septal regions, in a dose-dependent fashion (up to 500 microg/kg, p < 0.05, n = 34 - 40). beta-Sitosterol also enhanced the expressions of proteins related to angiogenesis, namely von Willebrand factors, vascular endothelial growth factor (VEGF), VEGF receptor Flk-1, and blood vessel matrix laminin (p < 0.05, n = 6). In addition, the intraperitoneal administration of beta-sitosterol at 500 microg/kg/day for a period of 19 days significantly improved the motion recovery of ischaemia/reperfusion-damaged gerbils as assessed by rota-rod testing (p < 0.001, n = 10). Our results suggest that beta-sitosterol has therapeutic angiogenic effects on damaged blood vessels.

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Power electronic DC to DC converters in plug-in hybrid and electric automotive applications demand high power bidirectional power flow capability, with wide input voltage range. Output voltage of energy storage devices like ultra capacitor or battery varies with the change in load. The converter needs to provide a successful voltage regulation on the load side for a wide range of input voltage. An isolated half bridge based converter is proposed in this project, with bidirectional power flow and minimum peak current for wide input voltage range through duty cycle, and phase shift control. The proposed converter has competitive total device rating with the conventional isolated bidirectional power converters. The converter uses the transformer leakage inductance as the primary energy transfer element. Proof of concept is realized through a small prototype.

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An automatic switching frequency tuning algorithm (ASTA) for a real-time condition is proposed. The primary aim is to maximize the power efficiency of a power electronic system. The power loss of a hard-switched power converter is determined by the power loss in power semiconductor devices, magnetic devices, capacitors, etc. Switching frequency of a power converter is one of the parameters which influence the power loss. The parameters which determine the maximum-efficiency point can vary with the ageing of devices and the change in environmental conditions. In this paper, a PWM-carrier frequency is utilized for efficiency maximization of a power conversion system. By varying the PWM-carrier frequency from the minimum to maximum value to search for the switching frequency associated with the point of maximum efficiency, this algorithm is designed for a hybrid-energy power conversion system which consists of DC/DC converters and a DC/AC inverter. For the realization of this algorithm, real-time power metering for efficiency calculations is realized by software, which requires no cost increase as the method shares the voltage-and-current sensing circuits with the converter control unit. The metering algorithm has tolerance of less than 1% over a wide load range. The experimental results present efficiency data captured during the operation of the ASTA algorithm in wide ranges of switching frequencies.