The International journal of applied radiation and isotopes最新文献

Cross sections per equivalent quantum (σ_q) have been measured for photonuclear reactions yielding ¹⁸F from LiF, SF₆, CF₄, Ne and metallic Na targets, in the energy range 77–125 MeV. The σ_q values for LiF and Na are conformable with known data, whilst the σ_q values for SF₆ and CF₄ are found to be 10% lower than for LiF. The utility of metallic Na as a target for ¹⁸F production has been demostrated by a nucleophilic substitution reaction with (C₂H₅)₄N¹⁸F, formed after dissolution of irradiated Na in absolute C₂H₅OH.

Scattering of 59.6 keV γ-rays of ²⁴¹Am from sodium iodide, aluminium and copper have been determined for scattering angles between 24 and 144°. Differential coherent plus incoherent scattering cross section values for copper have been obtained theoretically, by means of form factor and scattering function calculations. Comparing the experimental data with the theoretical cross section values for copper, the experimental arrangement has been calibrated for each scattering angle. So, absolute values of differential cross section of sodium iodide for 59.6 keV γ-rays for eleven scattering angles have been obtained.

A clinical electron linear accelerator was adapted for continuous energy selection and used to measure bremsstrahlung yield for the photonuclear reaction ²⁷Al (γ, 2p) ²⁵Na from 24.0 to 32.0-MeV in 0.25 MeV steps. A germanium detector was used to measure the number of photoproduct γ-rays emitted. The yield values were analyzed for photonuclear cross section using PHONUC II, a program especially adapted for use with yield data from thick-target bremsstrahlung. The cross section shows distinct resonance peaks at 26.3±0.3, 27.3±0.4 and 30.3±0.5 MeV. Possible theoretical origins of these resonances and applications of the reaction in accelerator energy calibration are discussed.

The DNA ligand Hoechst 33258 has been iodinated with carrier-free [¹²⁵I]iodide by the lactoperoxidase method. The product was separated from other iodination products and the uniodinated compound by preparative thin layer chromatography. ¹²⁵I-labelled Hoechst 33258 is useful as a probe with DNA molecules of defined sequence since the decay of the ¹²⁵I atom results in the induction of a double-strand break, the location of which can be detected by DNA-sequencing techniques.

The oxygen isotopic content of natural and heavy water has been determined by mass spectrometric analysis of oxygen gas, produced by direct chemical oxidation using either Na₂S₂O₈ in strongly basic media or ClF₃. The results from the two methods are in good agreement. No evidence for mass independent isotope fractionation effects in deuterium-free water or in heavy water samples from a variety of sources was found. The ¹⁷O and ¹⁸O content of three IAEA water standards (V-SMOW, GISP and SLAP) are reported.

Cross sections for the Cu(p, x) ⁵⁸Co, ⁶³Cu(p, 2n) ⁶²Zn and ⁶⁵Cu(p, n) ⁶⁵Zn reactions were measured in the energy region from 4 to 33 MeV. The excitation functions for ⁵⁸Co, ⁶²Zn and ⁶⁵Zn were determined and compared with the published data. The experimental cross sections have been used as reference data for proton beam monitoring in the energy range of 13–33 MeV.

This paper describes a convenient, high-yield synthesis of [¹⁸F]4-fluoroantipyrine, a blood flow tracer, by fluorination of antipyrine with [¹⁸F]acetylhypofluorite prepared in situ. The radiopharmaceutical was obtained in a radiochemical yield of 28 and 30% following HPLC and Sep-Pak purification, respectively. The two different purification procedures of the crude reaction are described. Sep-Pak filtration, after decomposition of the intermediary of the fluorination reaction by heating with NaOCH₃ in CH₃CN, produced a radiopharmaceutical with radiochemical purity of more than 98%. The synthesis requires 50 min following irradiation.

The ash content of coal can be determined by a technique based on pair production (PP). The PP technique has been previously proved in the laboratory and in the field, and five commercial PP gauges are in routine use at coal washeries in Australia. However for some applications on coals of highly variable ash composition, there is a need for improved accuracy.

Calculations and experiments have been made to investigate two methods of improving PP gauge accuracy for coals with highly variable ash composition. The first combines the PP gauge measurement with measurements of the low-energy part of the PP gauge spectrum and the second is done in conjunction with separate low and high energy γ-ray transmission measurements. Calculations show that these methods can correct the PP gauge assay exactly when the concentration of a single high-Z element in the ash varies. When more than one element varies, the error reduction is less and depends on the elements and their variations. Experiments with a group of samples from Blackwater, Queensland showed that gauge accuracy improved by about 20% relative using the first method. Use of the second method on two groups of samples from Blackwater and South Africa produced about 15% improvement. There was no reduction in error when either method was used on a third group of samples from the Hunter Valley, New South Wales.

Excitation functions were measured by the stacked-foil technique for the reactions ⁷⁶Se(p, n)⁷⁶Br, ⁷⁶Se(p, 2n)⁷⁵Br, ⁷⁶Se(p, 3n)^74mBr, ⁷⁶Se(p, α)⁷³As, ⁷⁶Se(p, αn)⁷²As, ⁷⁶Se(p, α2n)⁷¹As and ⁷⁶Se(p, ³He + 2pn + pd)⁷⁴As on 96.48% enriched ⁷⁶Se up to E_p = 40 MeV. The optimum energy range for the production of ⁷⁵Br via the ⁷⁶Se(p, 2n)⁷⁵Br reaction at our compact cyclotron is E_p = 24 → 21.5 MeV, the calculated thick target yield of ⁷⁵Br amounting to 32 mCi/μ Ah and the expected level of ⁷⁶Br-impurity to 2.0%. A thin layer of metallic ⁷⁶Se on Al-backing was used as target in combination with a water-cooled rotating target head. A dry distillation technique for the separation of radiobromine from irradiated targets was developed; radiochemical yields of about 40–52% were obtained. Using a 50.2 mg/cm² thick target (E_p = 24→21.85 MeV, an irradiation time of 1.25 h at a nominal proton beam current of 15 μA and a distillation time of 30 min at 300°C, about 160 mCi of ⁷⁵Br (at EOB) is produced. The total loss of ⁷⁶Se after irradiation and distillation process is <1%. The levels of ⁷⁶Br and ⁷⁷Br impurities in ⁷⁵Br are <3% and 0.15%, respectively.

A series of 7 indiumdialkyldithiocarbamates (R = ethyl, n-propyl, i-propyl, n-butyl, i-butyl, (CH₂)₅, (CH₂)₂O(CH₂)₂) has been prepared by reacting InCl₃ with aqueous solutions of the ligands. The products have been investigated at various concentration levels. The properties of the products at the lower concentration levels have been studied by thin-layer chromatography, electrophoresis and by determination of the octanol/water partition. A comparison of the results with the behaviour of the well-characterized tris(dialkyldithiocarbamato)indium(III) complexes is given.