The solid state track detector of celluloid films (cellulose nitrate+camphor 25% an weight) using etching technique is suitable for low energy alpha particle detection. The critical rate of energy loss for track formation in celluloid films is determined as 1.3 MeV/mg⋅cm2. Irradiated samples are etched in NaOH (6 N) solution at 46°C for 10 minutes. The etched tracks are observed under a view of optical microscope at magnification of 7×20-7×40. Under vacuum condition of 10-3 Torr or at low temperature of -26°C no changes are observed in track formation. The feature of track fading phenomena is different in hot water and air circumstances.
In a previous paper, a rapid nondestructive method to determine sulfur in petroleum products with 14 MeV neutrons was reported. The correction for oxygen, the predominant interfering element, was made, but the results showed a little positive bias. In the present paper, further experiments with the error are described, together with a counting technique and the precisions. It is shown through a calculation that, in the case of middle east crude oils, nitrogen has a great contribution to the bias; this is experimentally confirmed by the decay curves for three crude oils (each-Saran, Kuwait, and Khafji) and three commercial products (gas oil, and light and medium fuel oils) and by their spectra. Accordingly, a counting technique which chiefly reduces the effect of nitrogen is adopted. The biases observed in this way are +0.06 S% for the gas oil, +0.09 S% for the light fuel oil, and +0.11 S% for the medium fuel oil. The relative standard deviations are 2.4% for the medium fuel oil containing 2.40 %S and 7.4% for the gas oil containing 0.54%S.
The measurement of line spread functions for the combinations of certain X-ray films and lead foil screen in industrial γ-ray radiography was studied to get spatial frequency responses of such combinations. The measurement of line spread function requires a slit width as smaller as possible, but usually not so finite a slit width is adopted by technical reasons. To get the true line spread functions deducing from the observed radiographic image of the finite slit, the application of adequate approximate equation to the line spread function is necessary. Assuming that the line spread function is expressed by Gaussian curve and applying a simple correcting equation for slit width, authors determined the line spread function for γ-ray beams incident on the test film and having an intensity distribution expressed by Dirac's delta function. If γ-ray source is placed inside the area seeing the slit, the resultant line spread intensity indicates the same profile as it is at the center of this area, and in this case, other experimental errors are predominant. Response functions and the true line spread functions for the combinations of X-ray film and Co-60, Cs-137 and Ir-192 sources were shown. By the calculation from the normalized line spread function, the inherent unsharpness defined by step edge image was also shown. As a result, the unsharpness values of 280, 230 and 160 micron were obtained respectively for Co-60, Cs-137 and Ir-192.
To distinguish the distribution of double tracers, tritium and any other β-emitters, on the same autoradiogram, a special type of two-layer emulsion with incorporated different color coupler was introduced (Fig. 1) . Thirty two kinds of film with different sensitivity and thickness of the layers and different couplers were prepared to find a suitable set of the conditions. In principle, the outer layer, adjacent to the sample, should he sufficiently thick to prevent the penetration of the inner layer by tritium β-particles. On the other hand, to obtain a better distinction between tritium and other soft β-emitter, the outer layer must not be colored significantly by β-particles from the latter nuclide. This difficulty could be resolved by i) reducing the sensitivity of the outer layer to approximately one tenth to that of the inner layer, ii) placing an inter layer of gelatin (7μ thickness) between the two layers, and iii) increasing the thickness of the inner layer (11-12μ) as compared to that of the outer layer (4-6μ) . Three types of film were thus obtained (Table 1) . According to the difference in energy, tritium colored the film in cyan, while any other β-emitters in red (Type 24) or in yellow (Type 32) . In film Type 29, 3H colored it in cyan, 14C in green, and32P in yellow, providing a possibility of distinction of three nuclides. Applications of these films for identification of nuclides on thin-layer chromatogram and for tracing the distribution of double tracers in whole body autoradiography were examplified. A possibility of quantitative determination of two nuclides with densitometry was also discussed.
The distribution of3H or14C-labelled AV was studied by whole body autoradiography in mice. The labelled AV was administered to mice by intraperitoneal, intravenous, subcutaneous and oral route and each distribution pattern was discussed. In any administration route, AV and/or its metabolites were highly accumulated in such tissues as the liver, kidney, lung, brown fat, salivary gland, harderian gland, gall bladder, gastrointestinal tracts and urinary bladder. This compound also revealed to be accumulated in brain at the first after intravenous injection and to be easily absorbed from the digestive tracts. Almost of AV and/or its metabolites were excreted in urine and feces within 24 hours after administration and retention of radioactivity was not observed in any tissue. The radioactive substances passed the placental barrier but radioactivity in fetuses was lower than that in maternal tissues.