Synergism by coassembly at the origin of ion selectivity in liquid-liquid extraction.

In liquid-liquid extraction, synergism emerges when for a defined formulation of the solvent phase, there is an increase of distribution coefficients for some cations in a mixture. To characterize the synergistic mechanisms, we determine the free energy of mixed coassembly in aggregates. Aggregation in any point of a phase diagram can be followed not only structurally by SANS, SAXS, and SLS, but also thermodynamically by determining the concentration of monomers coexisting with reverse aggregates. Using the industrially used couple HDEHP/TOPO forming mixed reverse aggregates, and the representative couple U/Fe, we show that there is no peculiarity in the aggregates microstructure at the maximum of synergism. Nevertheless, the free energy of aggregation necessary to form mixed aggregates containing extracted ions in their polar core is comparable to the transfer free energy difference between target and nontarget ions, as deduced from the synergistic selectivity peak.

[High-frequency ultrasonic studies of peripheral circulatory behavior during anesthesia. 1st results with a new measurement procedure]. / Hochfrequenz-sonographische Untersuchungen des peripheren Blutströmungsverhaltens während der Anästhesie. Erste Ergebnisse mit einem neuen Messverfahren.

A new measurement system, based on high-frequency ultrasound Doppler shift detection, was developed to yield semiquantitative information on blood flow velocity in peripheral vascular compartments during anaesthesia. In 25 patients, anaesthetized by mask or intubation techniques, by this device blood flow velocity in the finger tips was recorded simultaneously with other physiological and haemodynamic parameters. In all patients characteristic changes in blood flow velocity were shown very consistently corresponding to different phases of the anaesthetic course. The graphic display of the Doppler shift frequency as an analogue signal yielded a continuous record of pulsatile blood flow velocity, while histograms on a TV-monitor showed its spectral distribution. Medications as well as stimuli from the area of surgery could be shown to reproducibly regarding course and depth of anaesthesia. The high sensitivity of this new monitoring technique producing semiquantitative data offers to the anaesthesist a reliable interpretation of the patient's intraoperative condition.

[Clinical experience with methohexital-nitrous oxide anaesthesia (author's transl)]. / Klinische Erfahrungen mit Methohexital-Natrium-Infusionsnarkosen.

The effects of methohexital, given as a 0.1% intravenous drip in combination with nitrous oxide were studied in 159 persons who had various types of surgical operations. The depth of anaesthesia was easily controlled, the circulation remained unaffected and the combination was well tolerated. There were no difficulties concerning either induction or recovery. The combination of i.v. methohexital and nitrous oxide proved very satisfactory for maintaining prolonged anaesthesia in elderly persons and patients in poor general health.