Comparison between a new acceleration transducer and a conventional force transducer in the evaluation of twitch responses

An acceleration transducer elicits an output voltage proportional to the deformation of the piezo crystal, in accordance with the twitch responses of the applied fingers. The reliability of such a transducer was evaluated by comparing induced twitch responses with those from a force transducer applied on the contralateral arm of an individual during neuromuscular block with vecuronium. The results obtained from twitch responses with the acceleration transducer during neuromuscular block were almost identical to those obtained with the force transducer. Also, the twitch heights due to acceleration of the examined thumb correlated extremely well with the twitch height due to twitch tension with the force transducer. It is concluded that the acceleration transducer may be a useful and reliable device for monitoring neuromuscular block, although responses during tetanic stimulation such as tetanic fade cannot be determined by the transducer.

Mirrorless dispersive optical bistability due to cross trapping of counterpropagating beams in sodium vapor

We report the first observation to our knowledge of mirrorless optical bistability based on a dispersive effect, namely, cross-trapping optical bistability due to the mutual interaction of two counterpropagating beams. The phase conjugation of a probe beam generated by four-wave mixing in such a system is sensitive to the intensities of the counterpropagating beams and has been used to monitor the bistability.

Observation of continuous-wave on-resonance "self-focusing"

We report what to our knowledge are the first observations of an increase in the on-axis intensity of an intense cw on-resonance beam resulting from nonlinear absorption and diffraction during its propagation through a highly absorbing medium (sodium vapor). This "self-focusing" is not a self-lensing; instead it is modeled well by placing an aperture part way through the cell: The stripping by the aperture approximates the effect of the nonlinear absorption, and then Fresnel diffraction results in on-axis minima and maxima.

Optical cross talk between nearby optical bistable devices on the same étalon

This Letter is concerned with the parallel operation of optical bistable devices. The two-beam side-by-side case has been simulated numerically. Diffraction coupling from one device operating in the upper branch can cause the other one, operating in the lower branch, to switch to the upper branch if the separation of the two beams is too small. The separation required for independent operation is usually a few beamwidths. The results give promise for performing parallel operations with optical bistable devices on the same étalon.

Neuromuscular effects of i.a. infusion of lignocaine in man

Neuromuscular effects of lignocaine during and after i.a. infusion were studied in healthy adult patients, using evoked electromyography. Supramaximal, paired stimuli were applied to the ulnar nerve with variable intervals between the two stimuli. The amplitude of the hypothenar muscle action potential to the second component of the paired stimulus (test response) was compared with that evoked by the first component (conditioning response). During and after i.a. infusion of lignocaine, there were marked decreases of the test response at intervals from 7 to 100 ms after the conditioning stimulus, although the decreases of the conditioning response were slight or negligible. The finding of decreased test responses coincided with the results obtained with tetanic stimulation such as pronounced fade and only slight post-tetanic potentiation. Differences between these findings and those found with muscle relaxants were compared, and it was concluded that the mechanism responsible for these results might be attributed to an effect of lignocaine on the motor nerve terminal.