Radio Instability

The initial hope for conducting polymers was that they would replace metals in applications as simple conductors. The interest for conducting coatings and radio-frequency shielding remains, but is so far held up by problems of instability and cost. Much work in this area is not published because it is carried out by the defence industries. 

Our data also indicate greater stability of the amino acids in beef than was observed in the case of 7-ray irradiation of insulin. In the latter case, Drake et al. (8) found that in addition to cystine, tyrosine, phenylalanine, proline, and histidine were quite radio sensitive. Instability of tyrosine in proteins on 7-ray irradiation has also been reported by Hatano (16), who states that in protein, tyrosine is the most sensitive amino acid. Kolo-miichenko and Morozova (24) found about 20% destruction of tryptophan, tyrosine, and histidine following 1.5 Mrads 7-ray irradiation of egg albumin. 

Because fluorescence detection by repeated absorption-emission cycles is not applicable to trapped molecular ions in UHV, that is, in the absence of collisions with a buffer gas [68], different techniques are required for their reliable identification. A commonly used destructive technique for molecular ions is time-of-flight (TOP) mass spectroscopy. We have used a simplified variant in the Ba+ apparatus. The trapped ions are extracted from the trap by reducing the radio-frequency amplitude, in the presence of a finite dc quadrupole potential Vo, which causes the ion trajectories to become unstable (the Mathieu -parameter enters the instability region). Heavy and hot ions escape first. Upon leaving the trap, the ions are guided to and attracted by the cathode of a channel electron multiplier (CEM) and counted. 

Gratzke et al [45] rejected the thermocapillary mechanism and proposed that humping and undercutting were caused by Rayleigh instability, i.e. the break-up of a liquid cylinder by the action of surface and gravity forces. They concluded that (i) the (width/length) radio of the pool was the most important factor and (ii) the surface tension does not affect the onset of humping, only the kinetic behaviour which is a function of (p/y) - The latter conclusion would seem to be inconsistent with the observation that it was prevalent in HS casts. 

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