Factors Affecting the Stability of Chlortetracycline, Tylosin and Furylfuramide Against Low Level of Ionizing Radiation

SUMMARY— Effect of low levels of ionizing radiation (0.01–0.2 Mrad) on the stability of chlortetracycline (CTC) , furylfuramide (FF) and tylosin (Tl) were investigated. Tl in the phosphate buffer of pH 6–8 was very sensitive to low-level radiation, while either FF or CTC exhibited fairly high resistance at the same dose levels. Removal of dissolved oxygen in the test solution by aerating with nitrogen gas enhanced the inactivation of TI and FF at 0.05–0.1 Mrad of radiation, but it had an opposite effect on the inactivation of CTC. Much higher TI and CTC activities were retained after irradiation at 0.1 or 0.2 Mrad when the drugs were added to albumin, gelatin, broth or minced meats of five species of fish; the retention of FF did not change.
The remaining activity of Tl at 0.1 or 0.2 Mrad of radiation was more or less influenced by adding various sugars and amino acids. The presence of sugars (mono- or disaccharides) did not change retention of TI markedly, but gave a weak protective effect. Tryptophane, histidine, phenylalanine, methionine and tyrosine exhibited a fairly high protective action on the inactivation of TI after irradiation.     

A negative hysteresis threshold circuit and its analysis†

It is well known that there is a hysteresis effect in the Schmitt trigger circuit. In the present paper, the author proposes a negative hysteresis threshold circuit which consists of a cathode-coupled trigger circuit with a CR delayed feedback loop. This circuit can be set to remove any hysteresis by adjusting the delayed feedback loop gain.

A non-linear analysis is developed on the above circuit, using the phase-plane method together with the experimental results.