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The mechanism of ambient pressure encapsulation of He and Ne in the R and β crystalline cages of type-A zeolites is demonstrated. Reversible and highly selective gas admission and entrapment are readily achieved at characteristic temperatures occurring between 77 and 570 K. The permeability of the zeolitic windows is governed by an interplay between the critical diameter of the encapsulate and the effective apertures dimension, which is shown to be strongly dependent on temperature. The blocking state of the zeolitic apertures is determined by a simultaneous thermal activation of both cation mobility and structural dilation/constriction of crystalline windows. Encapsulation in NaA (4A) principally occurs in the β cages of the Sodalite units, whereas the K-exchange form (3A) offers both R and β encapsulations. The effective free aperture dimension of the Ca exchange form (5A) is found to be too large to allow a practical gas enfoldment in either class of cavities, even at 77 K, where only poor encapsulation is observed. The counterion location vs size dependence, known only from crystallographic data, is sensed here for the first time by an encapsulation process, via the manifestation of different aperture occupancy states. While the blocking extent of the wider O 8 windows of the R cages is consistent with the size of exchangeable cations, a reverse correlation is evident for the narrower O 6 windows of the β cages.

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Myotonic dystrophy, a rare genetic disorder, may pose a serious problem to the anaesthesiologist due to muscular and extramuscular involvement. Thirteen patients, median age 21 yr were anaesthetized by continuous propofol infusion, fentanyl, atracurium and N2O to evaluate this combination in myotonic dystrophy. Intraoperatively, neither exaggerated reactions nor haemodynamic instability was observed. Recovery was smooth and quick. Although there was a significant decrease in mean postoperative vital capacity (965 (349) ml) from the preoperative value (1664 (566) ml, P = 0.0028), there was no change in mean postoperative SpO2 and there were no perioperative respiratory complications. Only two patients complained of nausea and vomiting. Similarly, muscular hypertonia and shivering were not observed. We conclude that the combination of continuous propofol infusion and fentanyl was a successful anaesthetic technique in these young myotonic dystrophy patients undergoing peripheral surgery.

High-gradient insulators HGI are periodic assemblies of conducting and insulating layers that have been shown to withstand higher pulsed voltages in vacuum than homogeneous insulators of the same length. We carried out calculations and experimental studies to understand the effect of geometry on the performance of wellconditioned, flat-surface HGI assemblies. We tested stacks with several different ( values of Ir r r r rM where I is the axial length of an insulating layer and M is the length ) of a metal layer . The experiments showed that HGI performance was substantially better than conventional insulators for Ir r r r rM -3 and somewhat worse for Ir r r r rM ) ) 3. Numerical calculations of electron orbits showed: 1 that the electric fields in HGI assemblies may have the favorable property of sweeping charged particles away ) from the surface and 2 that electron multiplication on the surface is suppressed when Ir r r r rM -3.Index Terms -High voltage insulators, electron avalanche, vacuum surface breakdown.