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This paper describes mathematical and software developments needed for the effective solution of differential algebraic equations of index 1 in the integrated computing environment MATLAB and the dynamic simulation package Simulink. The developments are applicable to other problem-solving environments and some are applicable to general scientific computation.

This paper describes mathematical and software developments for a suite of programs for solving ordinary differential equations in MATLAB.

The MATLAB ODE Suite is used as a case study for the development of ODE software in a new computing environment. Some current work on a multimedia project for teaching ODEs is used to illustrate another environment.

In the vanadium oxides V2O3, V3O5, and VO2 oxygen is partially replaced by the stable isotope O18. The concentration of O18 in the oxides is determined by IR spectroscopy. The resulting increase of the temperature Tc of the semiconductor—metal transition, found by the measurement of the electrical resistance, is discussed on the basis of different models of phase transition. The results can be qualitatively explained by a concept, where the transition is caused by electron—electron interaction, which is strongly modified by electron—phonon coupling. In den Vanadinoxiden V2O3, V3O5 und VO2 wird ein Teil des Sauerstoffs durch das stabile Isotop O18 ersetzt. Die Konzentration des O18 in den Oxiden wird durch IR-Spektroskopie bestimmt. Die resultierende Erhohung der Phasenumwandlungstemperatur Tc des Halbleiter—Metall-Phasenuberganges, die durch Messung des elektrischen Widerstandes ermittelt wurde, wird an Hand verschiedener Modelle fur den Phasenubergang diskutiert. Dieses Ergebnis kann qualitativ in einem Modell verstanden werden, in dem der Halbleiter—Metall-Phasenubergang durch die Elektron—Elektron-Wechselwirkungen verursacht wird, die durch die Elektron—Phonon-Kopplung stark modifiziert ist.

Das thermodynamische Verhalten des Systems VOTeCl wird beschrieben. Von besonderer Bedeutung fur das Transportverhalten ist der O2-Koexistenzgleichgewichtsdruck. Fur die Beschreibung des Transportes unterhalb 700 °C ist die Existenz von TeOCl2 in der Gasphase Voraussetzung. Aus dem Zusammenwirken des O2-Koexistenzgleichgewichtsdruckes mit den diminierenden Gasphasenspezies konnen die Transportrichtung, die Transportrate und die Sauerstoffan- und -abreicherung der kristallisierenden Phase berechnet und vorausgesagt werden. VO2-Einkristalle unterschiedlicher Phasenzusammensetzung werden hergestellt. The chemical transport behaviour of the vanadium oxides from V2O3 to V2O5 with TeCl4 is described. The O2 coexistence equilibrium pressure is of especial importance for the transport behaviour. The existence of TeOCl2 in the gas phase is the premise for the description of the transport behaviour below 700 °C. The transport direction, the transport rate and the increase or decrease of the oxygen content in the deposited phase, respectively, are calculated from the cooperation of the O2 coexistence equilibrium pressure with the composition in the gas phase. Single crystals of Vo2 are obtained with different phase compositions.

Two cases of cardiac asystole and one case of severe bradycardia were seen following a single injection of suxamethonium in a series of 46 adult patients in whom anaesthesia was induced with fentanyl and etomidate. It is suggested that the vagomimetic effects of fentanyl and, possibly also of etomidate, may contribute to the enhancement of the bradycardic effects of suxamethonium.

Summary Sixteen children with transposition of the great arteries (TGA), ventricular septal defect (VSD), and left ventricular outflow obstruction (LVOO) underwent intracardiac correction. The atrio-ventricular relationship was concordant in all instances. The VSD was single in 1 3 and multiple in 2 patients. In one child a common ventricle was found. LVOO presented as valvular stenosis in 2 cases, subvalvular stenosis in 9 cases, and combined valvular and subvalvular stenosis in one case. Three patients had previously undergone banding of the pulmonary artery. Intracardiac correction consisted in atrial inversion according to the Mustard technique. In 11 cases complete closure of the VSD was achieved. Because of incomplete subpulmonary resection, in 4 instances the VSD remained only partially closed. In the child with a common ventricle, atrial inversion without closure of the ventricular communication was performed. LVOO was treated by valvulotomy, resection of subpulmonary stenosis, or debanding of the pulmonary artery. There were two early deaths and one late death. Because of a recurrent VSD and severe tricuspid incompetence, reintervention with VSD closure and tricuspid valve replacement was necessary in one case. All surviving patients (81%) are in good clinical condition, although only in 7 of them had the VSD initially been totally closed. The presented results of conservative correction are comparable to those after the Rastelli operation for TGA, VSD, and LVOO. It may be advantageous, particularly in the younger children, that with this hemodynamic repair no extracardiac conduit is required.

From 1973 through December 1980, 41 children with total anomalous pulmonary venous connection (TAPVC) were seen in our hospital, and 35 underwent surgery. The supracardiac type of TAPVC was found in 19 cases (46%), the intracardiac type in 6 infants (15%), the infracardiac type in 15 cases (37%), and the mixed type in one child (2%). Clinical and cardiac catheterization data demonstrated that children with the infracardiac type of TAPVC were referred very early in life and had the highest pulmonary artery pressures. Operation was performed in 35 cases, 15 of supracardiac, 6 of cardiac, 13 of infracardiac, and 1 of mixed type of TAPVC. Total in-hospital mortality was 39%, and was 28% in the operated children. The initial operative mortality of 71% in the years 1973 to 1975 has decreased to 18% in the last 5 years. Twelve of the surviving infants underwent re-catheterization showing excellent results. Only in one case, with additional aplasia of the left lung, did half-systemic pulmonary artery pressure persist. Corrective surgery offers the only chance of survival in most children with TAPVC. The operative risk can be reduced by increased surgical experience supported by optimal medical preparation of the patient. After adequate surgical correction long-term results appear to be excellent.

To define the role of vecuronium in the occurrence of bradyarrhythmia, haemodynamic changes after the induction of anaesthesia were studied in 96 patients undergoing coronary artery bypass grafting. Patients were assigned to one of six groups according to different combinations of induction agents (etomidate 0.3 mg kg-1 or thiopentone 3 mg kg-1, with fentanyl 0.003 mg kg-1; etomidate 0.4-0.5 mg kg-1 or thiopentone 4-6 mg kg-1, without fentanyl) and neuromuscular blocking drugs (vecuronium 0.112 mg kg-1, pancuronium 0.112 mg kg-1 or suxamethonium 1 mg kg-1). Anaesthesia was maintained with enflurane and nitrous oxide in oxygen. After initial diverse changes, heart rate decreased in all groups. Thirty minutes after intubation, the reduction of heart rate showed statistically significant differences between the different combinations of drugs: fentanyl-etomidate-vecuronium (group I) (the largest reduction) greater than etomidate-vecuronium (II) = fentanyl-thiopentone-vecuronium (IV) greater than thiopentone-vecuronium (V) = fentanyl-thiopentone-suxamethonium (VI) = fentanyl-etomidate-pancuronium (III). Five patients in group I, two in group IV and one each in groups II and V had a heart rate slower than 45 beat min-1, whereas a similar value was never seen in groups III and VI. These results indicate that vecuronium has a bradycardic effect. This effect is more pronounced in association with etomidate than in association with thiopentone, and is augmented by the addition of fentanyl.