This paper describes the characteristics of the after-effect of the halogen quenched counter studied by means of the 90Sr RI chopper and the pulsated X-ray beam of the Linac. The experimental results show that the after-effect of the halogen quenched counter is extremely different from the organic quenched counter in the way that the characteristic of the hologen quenched counter is independent of the radiation intensity. In more detail, the after-effect does not increase with the radiation intensity of a pulsated radiation beam even though the pressure of quenching gas (Br2) is as low as 0.05 Torr, and only the short-time after-effect which depends on the number of main discharge pulses was observed under a constant anode voltage. Accordingly, the halogen quenched counter maintains a steady state in the high intensity radiation if a corrective coefficient of the after-effect is given.
The nitrogen analysis of petroleum products by means of the 14N (n, 2n) 13N reaction with 14 Me V neutrons was investigated. In order to avoid the various errors caused by the variation of the neutron flux, a rotation method, in which both an unknown sample and a standard sample would be irradiated by the same neutron flux, was adopted. For hydrocarbon samples, the 12C (p, r) 13N and 13C (p, n) 13N reactions with recoil protons, matrix effects, have prevented the determination of a small amount of nitrogen. By a series of experiments on the relation between the effects and the compositions of hydrocarbons, it was found that the effects depend only on the weight fraction of carbon (Wc) . Furthermore, it was found that, in the narrow range of the Wc, the effects may be expressed by a linear equation of the weight fraction. This relation has made it possible to obtain the fairly good results for the sample whose Wc-value is known and the nitrogen content is more than 0.1%. This method is particularly suitable for the analysis of nitrogen in fuel oils because they contain some considerable amounts of nitrogen and have nearly equal Wc-value which is 85%. About 25 minutes were required for an analysis in the present experiment, but the time will considerably be shortened by increasing the neutron flux and improving the counting technique.
Since about one year and a half ago, we have attempted the renal scanning using new agents 113mInFe-compounds, for the purpose of decreasing exposure of the kidneys to radiation, and have found clinical usefulness of the renal scanning with 113mIn. One to one and a half milli-curie of several 113mInFe-compounds was injected into the vein of rats respectively and average concentration ratio (kidney-to-liver) of 113mInFe-DTPA ascorbic acid obtained from five rats was 8.5 at thirty minutes after the injection. Because of this high concentration ratio, 113mInFe-DTPA ascorbic acid is considered to be more suitable for the use in the renal scanning than other113mInFe-compounds. Eighty milli-grams of Probenecid were given to rats to block the renal filtration before injection of 113mInFe-compounds. There was a remarkable difference between before and after giving Probenecid, the kidneyto-liver ratio increased to 11.2 with rats. Clinically, there was also a noteworthy difference. The renal concentration at 30 min after the injection of 6 mCi of 113mInFe-DTPA ascorbic acid to normal subjects increased by 12% to 45% by giving Probenecid to the subjects, the value of which being 100% at 4 minutes after injection. The similar increase with 113mInFe-EDTA was 15%, from 41% to 56%. We give patients, for the time being, 500 mg of Probenecid per Os 30 minutes prior to the scan in an attempt to block the renal filtration of 113mInFe-compounds, and have obtained good images of the renal scanning in every case.