Design and modeling of a new electro hydraulic actuator

grantor: University of TorontoThis thesis addresses the issues of design and mathematical model identification of an advanced hydraulic system referred to as Electro Hydraulic Actuator (EHA). In the design part, insights into system design methodology are presented and used for the EHA prototype manufacturing. To get better knowledge of the system behavior, extensive open loop tests were performed. Test results are presented in the time and frequency domain, and it was concluded that system behavior is nonlinear. In the modeling part, a nonlinear mathematical model of the EHA is derived. Some of the unknown model parameters had to be identified experimentally by optimization. The last step in the system mathematical modeling was open and closed loop model validation using the experimental data. Proposed nonlinear mathematical model gives good correspondence with experimental data and can be used for system studying or controller design. Performed test show that the EHA system has high positioning accuracy (0.01mm), fairly high bandwidth (23 Hz with 20kg inertial load) and is easy to control. It shows significant benefits when compared to conventional hydraulic systems in the areas of control, efficiency and physical dimensions.M.A.Sc

The role of the placenta in adverse fetal outcomes associated with maternal cocaine use and cigarette smoking in pregnancy

grantor: University of TorontoThe inhibitory effect of cocaine and nicotine on placental amino acid transport, as a mechanism contributing to intrauterine growth restriction (IUGR), was investigated in the perfused human placenta and in pregnancies exposed to cocaine and cigarette smoke. 'In vitro' amino acid transfer toward the fetal side was measured in the absence, and in the presence of 1.2 [mu]g/ml of cocaine, 120 ng/ml of nicotine or both. Neither cocaine nor nicotine alone significantly inhibited alanine transport, while their combination did (p = 0.02). Significant inhibition of arginine transport was detected with nicotine (p = 0.007), cocaine (p = 0.01) and their combination (p = 0.01), whereas phenylalanine (p = 0.03, p = 0.04) and valine (p = 0.03, p = 0.04) transport was affected by cocaine and their combination, respectively. For glutamine, neither cocaine, nicotine nor their combination had a significant inhibitory effect. Maternal and fetal plasma amino acid levels were determined in 11 control and 16 drug-exposed pregnancies. The drug-exposed infants had a significant decrease of gestational age, birth weight, length and head circumference. The fetal/maternal plasma amino acid concentration ratios in the drug-exposed group showed a trend to decrease for most amino acids, with a significant decrease of taurine (0.007). In parallel, the characteristics of nicotine transplacental transfer and biotransformation were investigated in the 'in vitro' placenta perfusion model. Following the addition of nicotine (40 ng/ml) to the maternal circulation, distribution into placental tissue (0.43 ± 0.13 ng/ml/min) was three times higher than transfer to the fetal circulation (0.15 ± 0.1 ng/ml/min). The clearance of nicotine was approximately 90% that of antipyrine. There was no evidence of nicotine metabolism to cotinine. Furthermore, the effect of nicotine on hCG secretion was investigated. At a nicotine concentration of 40 ng/ml, no statistically significant reduction of hCG levels was observed. Together, these observations strongly suggest that capacity of cocaine and cigarette smoke to inhibit amino acid transfer across the placenta can be a mechanism to explain the high rate of IUGR observed in cocaine and cigarette smoke exposed pregnancies. In addition, the observation that nicotine readily crosses the human placenta with no evidence of metabolism suggests that nicotine has the potential to cause adverse affects on the developing fetus.Ph.D

Relationship between plasma melatonin levels and the efficacy of selective serotonin reuptake inhibitors treatment on premature ejaculation

Objectives: To examine the relationship between premature ejaculation and plasma melatonin levels, and assess the efficacy of selective serotonin reuptake inhibitors in treating premature ejaculation