[en] Lyoluminescence of various saccharides and of glutamine has been investigated by using a home made read-out system allowing a better control of the dissolution rate. The device has been tested by measuring the weight and dose dependence of D(+) mannose and the influence of the origin of the sample. The use of eosin B solutions as a solvent shows a substantial enhancement of lyoluminescence for dextrose and xylose. (author)

[en] A comparative study has been made of the reactions of recoil ¹¹C atoms with c-C₆H₁₂, C₆H₆ and C₆ (CH₃)₆. Use was made of group separations of labelled recoil products by HPLC techniques. Reaction mechanisms are discussed on the basis of primary reactions of ¹¹C atoms: 1,H-abstraction leading to ¹¹CH; 2, insertion into a C-H bond, leading to an excited carbene that can decompose or isomerize to a stable monomeric compound. Thermal singlet carbenes can also insert into the C-H bond of another molecule (yielding dimeric compounds) whereas in the case of C₆H₆, a triplet carbene can add to the aromatic ring (leading to the formation of higher polymers); and 3, addition to the aromatic ring of C₆H₆ can also lead to an excited carbene, but such a process is thought to be sterically hindered in the case of C₆(CH₃)₆. (author)

[en] A new method to determine the leakage rate from encapsulated radium sources is proposed. The method is based on the principle of enclosing the source to be tested in a hermetically sealed container and measuring the radon radioactivity growth in the container as a function of time. A cylindrical modified Lucas cell, designed and built in our laboratory, is used for measuring the radon which are done by ZnS(Ag) alpha scintillation counting and can be easily compared with existing standard for leak tests. Results obtained show the applicability of the method for leak testing for radon leakage from sealed radium sources. (author)

[en] The Fano factor for germanium cooled to 77.4 K has been determined from a semiempirical analysis of the measured energy resolution of a HPGe γ-ray spectrometer of active volume 113.2 cm³. Twenty nine γ-ray energies spanning the range from 14 to 6129 keV were used in this study. The dispersion due to incomplete charge collection was assessed experimentally by making measurements over a wide range of applied bias. Plots of the peak centroid shift and the peak width squared against the reciprocal of the voltage applied to the detector, were non-linear. Both exhibited plateaus for large applied voltages. Thus, by operating in the plateau region, the Fano factor could be extracted from the variation of the observed line width as a function of energy, while the detector was known to be functioning close to the position of perfect charge collection. The value of the Fano factor obtained in this work, averaged over the energy range 14-6129 keV, was 0.112 ± 0.001. It is recommended that more, high quality, measurements be made. (author)

[en] Gas mixture of helium and carbon monoxide was irradiated with electron beam from a Van de Graaff accelerator and emission intensities from excited CO and CO ion were measured as a function of pressure, concentration of carbon monoxide in wide ranges. The results are fitted with kinetic analytical formulae derived from simple competition reactions involving energy transfer process assuming steady state concentrations for intermediates, and reasonable agreements were obtained between the experimental results and those predicted in the range of reaction conditions studied in this work. (author)

[en] The effects of radiation source fluctuations and void distributions and fluctuations on void fraction determinations in two-phase-flow systems employing the radiation transmission technique are presented. These fluctuations and distributions result in an error which varies in a different manner with the amplitudes of the fluctuations. The variance of the probability density function of the error is independent of void fluctuations, but decreases with measurement time-intervals while the peak is determined by the distribution pattern but shifts with void fluctuation. (author)

[en] The general public receives the highest share of its annual average radiation exposure from natural sources. A worldwide significant increase in exposure comes from radium and its decay products. Prime sources for radon in the environment and in houses are subsoil and building materials. The concentration of radon/thoron decay products in the air is dependent on the concentration of aerosols or dust particles. The presence of radon/thoron and its daughter nuclides can be detected by pumping air through a membrane (Thomsen, 1982; Lamb, 1989). The concentration of radionuclides can then be determined using an alpha (α) counter. Radon/thoron gas and its radionuclides in the air were analysed in the various rooms in the biophysics laboratory. The vacuum pump was used to collect the air samples on soft tissue paper. (author)

[en] A simple procedural change for the synthesis of [¹⁸F]FDG has been used to recover [¹⁸O]water by direct distillation. The [¹⁸O]water thus recovered is reusable to produce [¹⁸F]fluoride without further purification. The recovery of [¹⁸O]water is reliable and our results are based on over 300 routine FDG preparations. The [¹⁸F]fluoride present in the target water is converted to potassium fluoride during the distillation and will be available for further reaction to complete the synthesis of FDG. The same procedure can be used to recover [¹⁸O]water in similar situations where [¹⁸F]fluoride is converted to potassium fluoride and in turn used to react with kryptofix for labelling other precursors. (author)

[en] Methodology applicable to the synthesis of no-carrier-added [O-methyl-¹¹C]alfentanil was developed. The sequence consisted of [¹¹C]methylation and propionylation of N-aryl-4-(hydroxymethyl)-4-(N-anilino)-piperidines 1a and 1c, followed by the chemoselective hydrolysis of bulk byproducts to facilitate isolation of the NCA carbon-11-labeled product by prep-HPLC. All three steps could be performed without isolation of intermediates in a single reaction vessel. (author)

[en] A large number of radioactive nuclides useful as tracers are produced in targets by high-energy heavy-ion irradiations. With the aim of developing automated methods of preparing multitracer solutions, we are investigating separation of radioactive nuclides by means of supported liquid membranes which are now being viewed with keen interest as an efficient analytical tool. Separation by supported liquid membranes is considered to be especially suitable for preparation of multitracer solutions. This paper describes successful removal of the target material Au from multitracers by means of TBP-decalin membrane supported on a microporous polytetrafluoroethylene sheet. (Author)