Propulsion Requirements for High-Speed Vehicles with Electrodynamic Suspension
The thrust force and power requirements for the propulsion of a vehicle with electrodynamic suspension (i.e., using superconducting magnets) are discussed. Acceleration thrust, magnetic drag, and aerodynamic drag are shown to lead to calculated power requirements of 8.0 MW under acceleration, and 5.2 MW for cruising at 300 mi/h. Aerodynamic and magnetic drag forces together produce acceptable passive deceleration characteristics. Propulsion requirements under normal operation and in emergency situations (i.e., unscheduled stops) are described. Propulsion systems are discussed, and it is concluded that the linear synchronous motor is most suitable for the proposed Maglev vehicle.
Electromagnetic Levitation
AN exhibit which has proved attractive at the Centennial Exhibition of the Dominion of New Zealand is showing an aluminium plate floating in air in a strong alternating-current field and frying eggs in a pan without visible means of heating and support. An iron core is concealed beneath a table top and excited by A.C. windings so arranged and connected that they produce alternating magnetic fields, toroidal in form, of high intensity and opposite polarity. An aluminium pan floats on this field with such definition of position that considerable effort is required to move it downwards or sideways. Heat generated in the pan, by currents induced by the field, does the cooking. It is very suitable as an exhibit for publicity purposes, but at present it does not look as if it has any practical application, as a very large electrical input is required to maintain a magnetic field of suitable form and intensity.
Pharmacokinetics of Mivacurium Isomers and Their Metabolites in Healthy Volunteers after Intravenous Bolus Administration
Background Previous studies report the pharmacokinetics of mivacurium isomers after an infusion using venous blood sampling. Although the extent of the mivacurium arterial‐venous gradient is not known, the sampling site is likely to influence mivacurium pharmacokinetic parameters because the drug is rapidly metabolized as it traverses the circulation. The objectives of this study were (1) to determine the pharmacokinetics of mivacurium isomers in healthy persons after intravenous bolus administration using intensive arterial blood sampling, and (2) to characterize the formation and elimination of mivacurium metabolites in human plasma. Methods Eight persons classified as American Society of Anesthesiologists physical status 1 or 2 who were scheduled to undergo elective surgery under balanced anesthesia received 0.15 mg/kg mivacurium chloride as an intravenous bolus. Arterial blood samples were collected every 10 s during the first 2 min and at frequent intervals for 4 h thereafter. Plasma concentrations of mivacurium isomers and their metabolites were determined by two stereoselective high‐performance liquid chromatographic methods coupled with fluorometric detection and noncompartmental pharmacokinetic parameters. Results Mean elimination half‐lives of the trans‐trans, cis‐trans, and cis‐cis isomers were 2.4, 2, and 28.5 min, respectively, with corresponding mean plasma clearances of 29.2, 45.7, and 6.7 ml [center dot] min‐1 [center dot] kg‐1. The volumes of distribution at steady state of the trans‐trans, cis‐trans, and cis‐cis isomers were 0.047, 0.054, and 0.189 l/kg, respectively. Plasma concentrations of monoester and alcohol metabolites peaked 25 s (median) after mivacurium injection, with half‐lives in the range of 90 min, except for the cis alcohol metabolite, which was only negligibly and transiently formed. Conclusions Substantial hydrolysis of mivacurium isomers by cholinesterases was confirmed by the rapid appearance of mivacurium metabolites in plasma. The intensive arterial sampling proved to be critical for the trans‐trans and cis‐trans isomers because the area under the curve between 0 and 2 min accounted for 75% and 86% of the total, respectively.