The effects of ketanserin, 40 mg/day (KE40) and 80 mg/day (KE80) on mean arterial pressure, lipids, lipoproteins, and circulating atrial natriuretic factor (ANF) were investigated in a 24-week controlled study in 29 patients suffering from mild to moderate hypertension. A significant decrease in mean arterial pressure (MAP) was observed after 18 weeks of therapy, accompanied by a 64% (P less than .05) and 80% (P less than .02) increase in circulating ANF levels with KE40 and KE80, respectively. There were no significant changes in mean total cholesterol, triglycerides, or cholesterol of the high density lipoproteins (HDL), low density lipoproteins (LDL), and very low density lipoproteins (VLDL) fractions. There was a significant increase in the mean apo B levels and consequently a slight but statistically significant decrease in the ratio of LDL C/B. It is concluded that both doses of KE are effective for monotherapy of mild to moderate essential hypertension. The drug sharply increases circulating ANF levels without significantly altering the plasma lipids. In contrast, by increasing the apolipoprotein B content of the LDL fraction, the beneficial cardiovascular effect of a lowered blood pressure may be partly blunted.
High precision solar trackers have a great importance for High Concentration Photovoltaic systems and Concentrating Solar Power plants. In the former, the trackers are used to keep the concentration photovoltaic modules perpendicularly regarding to the sun rays to reach their highest energy conversion efficiency. In the later, they are used to guide a set of heliostats to reflect solar energy on a receiver. The solar trackers must be high precision, autonomous, inexpensive and low maintenance systems. The aim of this work is to describe a cascade control strategy for solar trackers to decrease the sun tracking error in order to achieve the maximum conversion efficiency and reduce electricity production costs through solar energy. The proposed cascade controller follows a double loop topology in which an inner loop compensates for the disturbances in the motor driving the solar tracker before they affect the sun tracking outer loop. The performance of the proposed scheme is evaluated using an experimental prototype. A comparison is made between a standard single loop PI controller and the proposed cascade controller. The proposed methodology allows a tracking error of 0.014º.
Editor's Note: In Spring 2009, I posted an invitation on Candrama, the listserv for the Canadian Association for Theatre Research, inviting scholars and artists to share stories of their experiences, encounters, or reflections on celebrity culture in Canada. Here are some of the responses I received.
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