Co-production of 155Tb and 152Tb irradiating 155Gd / 151Eu tandem target with a medium energy α-particle beam.

INTRODUCTION: Four terbium isotopes 149,152,155,161Tb emitting various types of radiation can be used for both diagnostics and therapy. 152Tb emits positrons and is ideal for PET. 155Tb is considered a promising Auger emitter and a diagnostic pair for other terbium therapeutic isotopes. Several methods for the production of 155Tb using charged particle accelerators have been proposed, but they all have significant limitations. The restricted availability of this isotope hinders its medical applications. We have proposed a new method for production of 155Tb, irradiating enriched 155Gd by alpha particles. The possibility of simultaneous production of two isotopes of terbium, 152,155Tb, was also studied for more efficient cyclotron beam use. METHODS: Irradiation of 155Gd enriched targets and 155Gd / 151Eu tandem target with alpha-particles with an energy of 54 MeV was carried out at the U-150 cyclotron at the NRC "Kurchatov Institute". The cross sections of nuclear reactions on enr-155Gd were measured by the stack foil technique, detecting the gamma-radiation of the activation products. The separation of rare earth elements was performed by extraction chromatography with the LN Resin. 155Tb was produced via 155Dy decay. RESULTS: The cross sections for the 155,156Tb and 155,157Dy production were measured by the irradiation of a gadolinium target enriched with the 155Gd isotope with alpha-particles in an energy range of 54 → 33 MeV. The yield of 155Dy on a thick target at 54 MeV was 130 MBq/µAh, which makes it possible to obtain 1 GBq of 155Tb in 11 hour-irradiation with 20 µA beam current. The possibility of simultaneous production of 152,155Tb by irradiation of 155Gd and 151Eu tandem target with medium-energy alpha-particles is implemented. Optimal irradiation energy ranges of alpha -particles as 54 → 42 MeV for 155Tb and 42 → 34 MeV for 152Tb were suggested. Product activity and radionuclidic purity were calculated.

Cross section measurements of 151Eu(3He,5n) reaction: new opportunities for medical alpha emitter 149Tb production.

Method for production of alpha emitter 149Tb by irradiation of 151Eu with 70 MeV 3He nuclei is proposed. For the first time, the cross sections for the formation of isotopes 149,150,151,152Tb were measured experimentally using a stack foil technique in the 3He particles energy range 70 → 12 MeV. The thick target yield of 149Tb is 39 MBq/µAh, or 230 MBq/µA 149Tb at saturation. The optimal energy range from the point of view of radioisotopic purity is 70 → 40 MeV. At these conditions about 150 MBq/µA 149Tb can be produced in 8 hours irradiation, which is sufficient for therapeutic applications. The main impurities are 150Tb (~100% in activity) and 151Tb (~30% in activity). The proposed method surpasses its counterparts by the high content of the target isotope in the natural mixture and the simplicity of the radiochemical separation of 149Tb from the bulk target material.

[THE INDUCTION OF CD25 EXPRESSION IN Jurkat T CELLS].

The expression of an α-subunit of interleukin-2 receptor (IL-2Rα) was assessed by quantifying activation-induced upregulation of CD25 in IL-2-independent Jurkat leukemic cell line. It has been found that in growing Jurkat culture within 24 h, phytohemagglutinin (PHA, 5 µg/ml) or PHA in combination with 12,13-phorbol dibutirate (PDBu, 10(-8)M) increase the number of CD25+ cells to 32.3 ± 3.4% (n = 11) and 44.8 ± 8.6% (n = 6) respectively. Interleukin-2 (IL-2, 200 U/ml) alone or in combination with PDBu did not induce CD25 expression in Jurkat cells. All the tested stimulatory agencies affected neither the proliferation status no the growth of Jurkat cell cultures. In contrast to human blood T cells, WHI-P131, a selective pharmacological inhibitor of JAK/STAT signaling and CD25 expression, did not decrease the number of induced CD25+ cells in Jurkat culture. Flow cytometry analysis revealed a dose-dependent decrease in the proportion of cells in G1 phase and an increase in the proportion of cells in G2/M phase in WHI-P131-treated Jurkat cultures. It has been also found that WHI-P131 induces G2/M arrest in the absence of PHA or PDBu. We have concluded that (1) the IL-2-independent T cells of Jurkat line had not loss the mechanism for IL-2Rα expression in response to T cell receptor activation, (2) in the transformed T cells, WHI-P131 can arrest cell cycle at G2/M phase and has effects on targets other than IL-2 receptor-associated tyrosine kinase JAK3.

Chemical characterization of element 112.

The heaviest elements to have been chemically characterized are seaborgium (element 106), bohrium (element 107) and hassium (element 108). All three behave according to their respective positions in groups 6, 7 and 8 of the periodic table, which arranges elements according to their outermost electrons and hence their chemical properties. However, the chemical characterization results are not trivial: relativistic effects on the electronic structure of the heaviest elements can strongly influence chemical properties. The next heavy element targeted for chemical characterization is element 112; its closed-shell electronic structure with a filled outer s orbital suggests that it may be particularly susceptible to strong deviations from the chemical property trends expected within group 12. Indeed, first experiments concluded that element 112 does not behave like its lighter homologue mercury. However, the production and identification methods used cast doubt on the validity of this result. Here we report a more reliable chemical characterization of element 112, involving the production of two atoms of (283)112 through the alpha decay of the short-lived (287)114 (which itself forms in the nuclear fusion reaction of 48Ca with 242Pu) and the adsorption of the two atoms on a gold surface. By directly comparing the adsorption characteristics of (283)112 to that of mercury and the noble gas radon, we find that element 112 is very volatile and, unlike radon, reveals a metallic interaction with the gold surface. These adsorption characteristics establish element 112 as a typical element of group 12, and its successful production unambiguously establishes the approach to the island of stability of superheavy elements through 48Ca-induced nuclear fusion reactions with actinides.

[On the influence of silicate feeding on metabolism of 137Cs in rabbit]. / O vliianii kormovogo ispol'zovaniia silikatov na metabolizm 137Cs v organizme krolikov.

The features of 137Cs metabolism in the rabbit's organism when feeding on silicates were investigated. By results of two experiments on rabbits radiosorption by of zeolite, saponit, humolit, vermiculite and palygorskit in the gastrointestinal tract was evaluated. It was found that vermiculite and palygorskit had the strongest influence on processes of accumulation and decorporation 137Cs, when a dose of additives was 5% of the weight of forage.