Influence of texture and grain misorientation on the ionic conduction in multilayered solid electrolytes - interface strain effects in competition with blocking grain boundaries.

Interface strain and its influence on the ionic transport along hetero-interfaces has gained a lot of attention over the last decade and is controversially discussed. We investigate the relaxation of mismatch induced interfacial strain as a function of the degree of orientation/texture of the columnar crystallites and assess the impact on the oxygen ion conductivity in Er2O3/YSZ multilayer systems. Results from X-ray diffraction clearly show, that the width of the strained hetero-interface region increases with an increasing degree of orientation of the crystallites. The combined impact of film texture and strain at the hetero-interfaces of the film on the ionic conductivity however is not easily deduced from these measurements. The samples with the highest degree of orientation, i.e. with only one azimuthal variant, show strong anisotropic electrical properties. In samples with a lower degree of orientation, i.e. samples with a fiber texture, anisotropic properties cannot be detected, possibly due to a geometrical averaging of the electrical properties. The expected strain induced monotonic increase of the ionic conductivity with decreasing layer thickness and thus increasing interfacial influence could only be detected for samples with a fiber texture and a considerable degree of crystallite misorientation. This leads to the important conclusion that the texture and therefore the nature of the grain boundaries and their network influence the ionic conductivity of the multilayer thin films in the same order of magnitude as the misfit induced interface strain. Thus, the potential design of strain-controlled ionic conductors requires additionally the control of the microstructure in terms of grain orientation.

Vasodilatory effects of nisoldipine on coronary arteries--correlation with plasma levels.

Vasomotion of angiographically normal and stenotic epicardial coronary arteries was analyzed up to 15 minutes after the onset of an intravenous infusion (4 minutes) of 0.5 mg (13 patients, group A) or 1 mg nisoldipine (13 patients, group B). After both doses the maximal increase of the mean diameters of normal coronary segments was achieved not before the 15th minute, averaging 11 +/- 6% in group A (p less than 0.001) and 18 +/- 9% in group B (p less than 0.001). Eleven of 15 and 8 of 9 coronary stenoses in groups A and B dilated to 5-80% and 15-70%, respectively. The nisoldipine concentration reached maximal levels at the end of the infusion (fourth minute) with an average of 8 +/- 4 ng/ml and 17 +/- 7 ng/ml in groups A and B, respectively. A significant correlation between nisoldipine plasma levels and dilation of normal coronary segments was obtained only with the individual maxima of these parameters and only in group A (p less than 0.01). The hysteresis of the coronary dilation in relation to the drug plasma levels may be due to the high receptor affinity of nisoldipine. In either group nisoldipine provoked a persistent increase in coronary sinus oxygen saturation (p less than 0.01) and a substantial and prolonged drop in systolic and diastolic aortic pressure (p less than 0.001). Both doses of nisoldipine induced a rise in heart rate (p less than 0.01) and a slight drop in the rate-pressure product (p less than 0.05).

Coronary vasodilation with dihydropyridines--a pharmacokinetic study.

In 26 patients with coronary artery disease, the mean diameters of angiographically 'normal' epicardial coronary arteries were assessed with the aid of a computer-assisted contour detection system (CAAS) before and up to 15 min after onset of a 4-min intravenous-infusion of 2 mg nifedipine (13 patients, group I) or 1 mg nisoldipine (13 patients, group II). Maximal coronary dilation amounted to 20 +/- 9% (4th min) in group I and to 18 +/- 9% (15th min) in group II. In addition, in group II changes of the minimal diameters of 9 coronary obstructions were measured; the maximum increase averaged 28 +/- 15% (7th min). In order to compare the pharmacokinetic properties of these compounds the dilation of the 'normal' coronary segments was correlated with the respective drug plasma levels; maximal plasma concentrations averaged 62 +/- 21 ng ml-1 (7th min) in group I and 17 +/- 7 ng ml-1 (4th min) in group II respectively. A positive, linear correlation between coronary dilation and plasma levels was only found with nifedipine (P less than 0.05); with nisoldipine, however, coronary dilation developed in form of a hysteresis curve, when plotted against plasma levels, probably due to the high receptor affinity of this substance. The prolonged efficacy of nisoldipine could be favourable in oral long-term treatment of patients with coronary artery disease.