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[en] New experimental results on photo-excitation of the Cd and In spin isomers by real and virtual photons (electrons) in the threshold energy region are presented. Measurements have been performed using the INR electron linac LUE—8 MeV and, in parallel, the femtosecond laser facility of the Moscow State University. A detailed description of experimental methods based on the GEANT-4 simulation is done. The obtained data are discussed in frame of the phenomenological model which allows the theoretical evaluation of the isomeric ratio in this energy region. Contribution of the dipole and quadrupole mode excitations in Cd and In nuclei from measurements with real and virtual photons is discussed. (paper)
[en] The analogy between the isomeric of molecules and the shape isomeric of nuclei is shown and the main features of the fission isomers as halflives, probabilities of spontaneous fission and spins are discussed. Possible explanation of the nature of fission isomers, based on the Strutinsky model, is given. Subsequently, systematics of the halflives of fission isomers and their dependence on the neutron number for U - Cm isomers and on Z2/A for odd-odd, odd-proton, odd-neutron and even-even isomers is shown. Quite new approach to the problem, which is made possible by the existence of negative muons is considered. For some heavy elements e.g. 239Pu 25% of 2P-IS transitions are not accompanied by X-ray emission but the total energy of 2P-IS orbit is transferred immediately into the nucleus, the latter being excited to 6.5 MeV. These radiationless transitions considered as transitions of negative muons can be accompanied by formation of fission isomers. The isomeric level in the presence of a muon is expected to be shifted and the halflife will be changed. It is concluded that the search for gamma decay of shape isomers is still one of the most important problems as well as the U search for the new region of shape isomeric which is predicted by the Strutinsky model. (S.B.)
[en] A 119Sn Moessbauer study was carried out of tin(IV) complexes with 2-benzoylpyridine thiosemicarbazone (H2Bz4DH) and its N(4)-methyl (H2Bz4M) and N(4)-phenyl (H2Bz4Ph) derivatives: [Sn(2Bz4DH)Cl3] (1), [Sn(2Bz4DH)PhCl2] (2), [Sn(2Bz4M)Cl3] (3), [H22Bz4M]2[Ph2SnCl4] (4), [Sn(2Bz4Ph)PhCl2] (5), [Sn(2Bz4Ph)Ph2Cl] (6), in which H2Bz4R stands for the neutral ligand and 2Bz4R stands for the anionic thiosemicarbazone. In addition, 119Sn Moessbauer studies of the tin(IV) complexes [Sn(H4Bz4DH)2Cl4H2O] (7), [Sn(H4BzPS)2Cl4H2O] (8) with 4-benzoylpyridine thiosemicarbazone (H4Bz4DH) and the correspondent semicarbazone (H4BzPS) were performed. The isomer shifts decrease upon coordination due to the variation in the percentage of s character as tin changes from approximately sp3 hybridization in the tin salts to sp3d2 in the octahedral or sp3d3 in the heptahedral complexes. The Moessbauer parameters of compound (4) showed the existence of two tin(IV) sites, which have been attributed to the presence of the cis and trans isomers.
[en] Moessbauer parameters like isomer shift, quadrupole splitting and line width measured at liquid helium temperature for six isomer pairs of cis-trans Ir(III) complexes are reported. An 102Os/Nb source was used. The data obtained suggest that although the appearance of the two β picoline complexes was very different, the trans product being red and macrocrystal-line while the cis was a yellow powder, it is improbable that these are cis and trans isomers. The quadrupole splitting of the red product suggests both are trans species. (T.I.)
[en] We characterize Cesàro–Orlicz function spaces containing order isomorphically isometric copy of under some mild assumption imposed on the Orlicz function . We discuss also some useful applicable sufficient conditions for the existence of such a copy.
[en] Isocyanic acid (HNCO) is a well-known interstellar molecule. Evidence also exists for the presence of two of its metastable isomers in the interstellar medium: HCNO (fulminic acid) and HOCN (cyanic acid). Fulminic acid has been detected toward cold and lukewarm sources, while cyanic acid has been detected both in these sources and in warm sources in the Galactic Center. Gas-phase models can reproduce the abundances of the isomers in cold sources, but overproduce HCNO in the Galactic Center. Here we present a detailed study of a gas-grain model that contains these three isomers, plus a fourth isomer, isofulminic acid (HONC), for four types of sources: hot cores, the warm envelopes of hot cores, lukewarm corinos, and cold cores. The current model is partially able to rationalize the abundances of HNCO, HOCN, and HCNO in cold and warm sources. Predictions for HONC in all environments are also made.
[en] DNA minicircles of 207 bp were constructed by the ligation of linear restriction fragments in the presence of various concentrations of ethidium bromide. Three topoisomers characterized by linking numbers (Lk) of 20, 19 and 18, and with helical repeats of 10.35, 10.9 and 11.5 bp/turn respectively, were obtained. The three minicircles were irradiated with γ-rays of fast neutrons. The same yields of single-strand breaks, double-strand breaks and alkali-induced single-strand breaks were observed for the three topoisomers showing that their base and sugar moieties are attacked equally by γ photon-or fast neutron-induced radicals. We conclude that untwisting of a B helix does not modify the radiosensitivity of DNA. (Author)
[en] New isomers of Cn for n = 4, 5, 6, have been observed using a combination of the laser photodetachment technique of the Coulomb Explosion Imaging method. The electron affinities of these isomers were found to be lower than the corresponding known linear isomers. The structure of low electron affinity C4 isomer was found to be rhombic in accordance with recent theory. Indications of the non linearity of the low electron affinity isomers of C5 and C6 are also presented. (Author)