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Öğe Decreased nocturnal synthesis of melatonin in patients with coronary artery disease(Elsevier Sci Ireland Ltd, 2003) Yaprak, M; Altun, A; Vardar, A; Aktoz, M; Ciftci, S; Ozbay, GIn human beings, cardiovascular activity has a distinct circadian variation: Heart rate, blood pressure, and vascular tone decrease at night. Nocturnal cardiovascular blunting is at least partially linked to the autonomic activity and increased risk of cardiac and cerebral events. To assess whether decreased nocturnal melatonin synthesis and secretion in coronary artery disease (CAD), we investigated nocturnal secretion pattern of melatonin in patients with CAD and healthy subjects. The present study performed in 16 patients with angiographically documented CAD (aged 46-71 years) and in nine healthy controls (aged 36-66 years). Blood samples were collected every 2 h between 22:00 and 08:00 h. Melatonin levels were measured with a commercially available radioimmunoassay kit. We found large interindividual variation in the pattern of melatonin secretion in both groups. Patients with CAD secreted less nocturnal melatonin at 02:00, 04:00 and 08:00 h than control subjects (P=0.014, P=0.04 and P=0.025, respectively). Peak and A melatonin (peak-lowest melatonin) were found lower in patients with CAD (48.6 [19.1-75.4] vs. 131.4 [67.8-137.2] pg/ml, P=0.006 and 43 [10.5-68.5] vs. 107.6 [55.7-113.1] pg/ml, P=0.002, respectively). Peak time of melatonin secretion was observed earlier in patients with CAD (02:00 h [23:00-02:00 h] vs. 03:45 h [02:00-05:00 h], P=0.04). Our study provides useful and preliminary information about decreased nocturnal melatonin synthesis and release in patients with CAD might help physicians in managing these patients. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.Öğe Impaired nocturnal synthesis of melatonin in patients with cardiac syndrome X(Elsevier Sci Ireland Ltd, 2002) Altun, A; Yaprak, M; Aktoz, M; Vardar, A; Betul, U; Ozbay, GWe investigated nocturnal secretion pattern of melatonin in patients with cardiac syndrome X and healthy subjects. The present study performed in five patients with cardiac syndrome X and in nine healthy controls. Blood samples from all subjects were collected every 2 h intervals between 22:00 and 08:00 h. Melatonin levels were measured with a radioimmunoassay kit. Patients with cardiac syndrome X secreted less nocturnal melatonin at 02:00 h than control subjects (P = 0.04). Peak and Delta melatonin (peak-lowest melatonin) were found lower in patients with cardiac syndrome X (P = 0.039 and P = 0.028, respectively). In conclusion patients with cardiac syndrome X show a markedly decreased nocturnal melatonin synthesis. Our study provides useful information about melatonin synthesis and release in patients with cardiac syndrome X might help physicians in managing these patients. (C) 2002 Published by Elsevier Science Ireland Ltd.Öğe The wind tunnel measuring methods for wind turbine rotor blades(Techno-Press, 2004) Vardar, A; Eker, WIn this study, a wind tunnel, that has been developed for experiments of wind turbine rotor blades, has been considered. The deviations of the measurements have been examined after this wind tunnel had been introduced and the measurements on it had been explained. Two different wind turbine rotor blades miniatures have been used for getting better results from the experiments. The accuracy of measurements have been experimented three times repetitively and examined statistically. As a result, wind speed values which this type of wind tunnel and wind turbine rotors need for starting, wind speed in the tunnel, temperature and moisture values, the number of rotor's revolution, and the voltage that is produced in 102 Omega resistance and current values have been determined to be fixed by measurements used. This type of wind tunnel and wind turbine rotor' performance difference and the difference of revolution figures have been determined to be fixed by measurements used.
