Transient stability of a power system with superconducting fault current limiters

The influence of a superconducting fault current limiter (FCL) on the transient stability of the synchronic operation of electric machines is analyzed for different locations of the inductive FCL in a network and for different parameters of the device. It is shown that the stability can be improved or degraded depending on the FCL impedance under a fault and the time of the recovery of the initial state of the limiter after a fault. Improving the transient stability with the inductive superconducting FCL is demonstrated in the experiments on the electrodynamic model of a power system. The expansion of the obtained results for other FCL designs is discussed

A SPECIAL MOTION AND PERFORMANCE ANALYSIS OF PROFESSIONAL CYCLIST

The biomechanical analysis of sport-motion is a new joint research field of biomechanics and sport medicine. Each cyclist was examined at an own bike mounted on an ergometer for analyzing the motion and the muscle activity at different loading. The ultrasoundbased 3D motion analysis- system and surface EMG signals were used to measure the motion parameters during the cycling. The kinematical parameters, such as the knee angle, and the muscle activity of four muscle groups were determined in every cycle of pedaling. The lactic-acid amount of the capillary-blood and the pulse were checked during the exercise. On the basis of the analysis, it can be established that the movement and the muscle activity are disordered close to the anaerobic threshold; thereafter, they become ordered. The results o the examination give effective help to trainers and athletes to improve the performance

Different electrophysiological effects of the levo- and dextro-rotatory isomers of mexiletine in isolated rabbit cardiac muscle

Racemic mexiletine is a widely used antiarrhythmic agent which blocks sodium channels. The effects of R-(-) and S-(+) mexiletine stereoisomers on maximum rate of depolarization (Vmax), conduction time and repolarization have not yet been investigated in isolated cardiac preparations. We studied the effect of the R-(-) and S-(+) mexiletine on rabbit cardiac action potential parameters by using the conventional microelectrode technique. Both enantiomers at 20 microM of therapeutically and experimentally relevant concentration, significantly depressed the Vmax at fast heart rates (BCLs 300 - 700 ms). R-(-) mexiletine has more potent inhibitory effect than S-(+) mexiletine. Both R-(-) and S-(+) mexiletine significantly inhibited the Vmax of early extrasystoles measured at 70 ms diastolic interval induced by S1-S2 stimuli. R-(-) mexiletine has more pronounced inhibitory effect than S-(+) mexiletine. Both R-(-) and S-(+) mexiletine increased significantly the ERP/APD90 ratio. The time constant (tau) of recovery of Vmax was found to be tau = 376.0 +/- 77.8 ms for R-(-) mexiletine and tau = 227.1 +/- 23.4 ms for S-(+) mexiletine which indicates a slower offset kinetics for R-(-) mexiletine from sodium channels than that of the S-(+) enantiomer. These data suggest that R-(-) mexiletine might be more potent antiarrhythmic agent than S-(+) mexiletine

Hormonal Neuroendocrine and Vasoconstrictor Peptide Responses of Ball Game and Cyclic Sport Elite Athletes by Treadmill Test.

ObjectiveOur objective was to evaluate complex hormonal response in ball game and cyclic sport elite athletes through an incremental treadmill test, since, so far, variables in experimental procedures have often hampered comparisons of data.MethodsWe determined anthropometric data, heart rate, maximal oxygen uptake, workload, plasma levels of lactate, adrenaline, noradrenaline, dopamine, cortisol, angiontensinogen and endothelin in control (n = 6), soccer (n = 8), handball (n = 12), kayaking (n = 9) and triathlon (n = 9) groups based on a Bruce protocol through a maximal exercise type of spiroergometric test.ResultsWe obtained significant increases for adrenaline, 2.9- and 3.9-fold by comparing the normalized means for soccer players and kayakers and soccer players and triathletes after/before test, respectively. For noradrenaline, we observed an even stronger, three-time significant difference between each type of ball game and cyclic sport activity.ConclusionsExercise related adrenaline and noradrenaline changes were more pronounced than dopamine plasma level changes and revealed an opportunity to differentiate cyclic and ball game activities and control group upon these parameters. Normalization of concentration ratios of the monitored compounds by the corresponding maximal oxygen uptake reflected better the differences in the response level of adrenaline, noradrenaline, dopamine and cortisol