Spectroscopy of the heaviest nuclei (theory)

Recent progress in the applications of covariant density functional theory (CDFT) to the description of the spectroscopy of the heaviest nuclei is reviewed. The analysis of quasiparticle spectra in actinides and the heaviest A ~ 250 nuclei provides a measure of the accuracy of the description of single-particle energies in CDFT and an additional constraint for the choice of effective interactions for the description of superheavy nuclei. The response of these nuclei to the rotation is rather well described by cranked relativistic Hartree+Bogoliubov theory and it serves as a supplementary tool in configuration assignment in odd-mass nuclei. A systematic analysis of the fission barriers with allowance for triaxial deformation shows that covariant density functional theory is able to describe fission barriers on a level of accuracy comparable with the best phenomenological macroscopic+microscopic approaches.Comment: 10 pages, 7 figures, invited talk of A.V. Afanasjev at the International Nuclear Physics Conference (INPC 2010), Vancouver, Canada, July 4-9, 2010, to be published in Journal of Physics G: Conference Series (JPCS

Relativistic quasiparticle time blocking approximation. II. Pygmy dipole resonance in neutron-rich nuclei

Theoretical studies of low-lying dipole strength in even-even spherical nuclei within the relativistic quasiparticle time blocking approximation (RQTBA) are presented. The RQTBA developed recently as an extension of the self-consistent relativistic quasiparticle random phase approximation (RQRPA) enables one to investigate effects of coupling of two-quasiparticle excitations to collective vibrations within a fully consistent calculation scheme based on covariant energy density functional theory. Dipole spectra of even-even $^{130}$Sn -- $^{140}$Sn and $^{68}$Ni -- $^{78}$Ni isotopes calculated within both RQRPA and RQTBA show two well separated collective structures: the higher-lying giant dipole resonance (GDR) and the lower-lying pygmy dipole resonance (PDR) which can be identified by a different behavior of the transition densities of states in these regions.Comment: 28 pages, 13 figure

Microscopic description of the pygmy and giant electric dipole resonances in stable Ca isotopes

The properties of the pygmy (PDR) and giant dipole resonance (GDR)in the stable $^{40}Ca$,$^{44}Ca$ and $^{48}Ca$ isotopes have been calculated within the \emph{Extended Theory of Finite Fermi Systems}(ETFFS). This approach is based on the random phase approximation (RPA) and includes the single particle continuum as well as the coupling to low-lying collectives states which are considered in a consistent microscopic way. For $^{44}Ca$ we also include pairing correlations. We obtain good agreement with the experimental data for the gross properties of both resonances. It is demonstrated that the recently measured A-dependence of the strength of the PDR below 10 MeV is well understood in our model:due to the phonon coupling some of the strength in $^{48}Ca$ is simply shifted beyond 10 MeV. The predicted fragmentation of the PDR can be investigated in $(e,e')$ and $(\gamma ,\gamma')$ experiments. Whereas the isovector dipole strength of the PDR is small in all Ca isotopes, we find in this region surprisingly strong isoscalar dipole states, in agreement with an $(\alpha,\alpha'\gamma)$ experiment. We conclude that for the detailed understanding of the structure of excited nuclei e.g. the PDR and GDR an approach like the present one is absolutely necessary.Comment: 6 figure

Covariant theory of particle-vibrational coupling and its effect on the single-particle spectrum

The Relativistic Mean Field (RMF) approach describing the motion of independent particles in effective meson fields is extended by a microscopic theory of particle vibrational coupling. It leads to an energy dependence of the relativistic mass operator in the Dyson equation for the single-particle propagator. This equation is solved in the shell-model of Dirac states. As a result of the dynamics of particle-vibrational coupling we observe a noticeable increase of the level density near the Fermi surface. The shifts of the single-particle levels in the odd nuclei surrounding 208-Pb and the corresponding distributions of the single-particle strength are discussed and compared with experimental data.Comment: 27 pages, 8 figure

Certain features of using modified collagen-containing raw materials with prolonged shelf life in food technology

In the current circumstances, trends in nutrition of a person striving to lead a healthy life-style require intake of meat products with the reduced energy value, minimal amounts of fat, increased protein mass fraction, presence of substances improving homeostasis of the body. The synergism of the modern nutrition science and meat industry enables creating food products that satisfy consumers’ demand. Today, in the Russian Federation, a theoretical and practical base of the technology development has been collected to the full extent in the field of rational processing of secondary raw materials in the food industry, optimal use of animal secondary raw materials, study of the protein ingredients of animal and plant origin and their deep scientifically substantiated processing, improvement of technological processes and equipment, and correspondently, product range extension. The paper broadens the information about the modified collagen-containing raw materials (cattle rumen), examines physico-chemical characteristics of the collagen-containing raw material and its changes in the process of freeze-drying with a special attention paid to the study of changes in the histological structure. The presence of the relatively uniform fibrillar structure was determined, which facilitated discovering the functional potential of proteinoids that form the fibrillar matrix in the composition of products from different groups. Analysis of IR-spectra revealed several significant absorption bands linked with the state of peptide bonds. The character of bands is linked with the complex of valence and deformation vibrations of the N- and С- types. It is believed that IR-spectra reflect conformations in the protein secondary structure, which suggests preserving properties of the tropocollagen particle or collagen molecule. Freeze-dried modified collagen-containing cattle rumen was tested by the example of jellies. The obtained databank broadens information about physico-chemical properties of modified collagen-containing raw materials (cattle rumen).In the current circumstances, trends in nutrition of a person striving to lead a healthy life-style require intake of meat products with the reduced energy value, minimal amounts of fat, increased protein mass fraction, presence of substances improving homeostasis of the body. The synergism of the modern nutrition science and meat industry enables creating food products that satisfy consumers’ demand. Today, in the Russian Federation, a theoretical and practical base of the technology development has been collected to the full extent in the field of rational processing of secondary raw materials in the food industry, optimal use of animal secondary raw materials, study of the protein ingredients of animal and plant origin and their deep scientifically substantiated processing, improvement of technological processes and equipment, and correspondently, product range extension. The paper broadens the information about the modified collagen-containing raw materials (cattle rumen), examines physico-chemical characteristics of the collagen-containing raw material and its changes in the process of freeze-drying with a special attention paid to the study of changes in the histological structure. The presence of the relatively uniform fibrillar structure was determined, which facilitated discovering the functional potential of proteinoids that form the fibrillar matrix in the composition of products from different groups. Analysis of IR-spectra revealed several significant absorption bands linked with the state of peptide bonds. The character of bands is linked with the complex of valence and deformation vibrations of the N- and С- types. It is believed that IR-spectra reflect conformations in the protein secondary structure, which suggests preserving properties of the tropocollagen particle or collagen molecule. Freeze-dried modified collagen-containing cattle rumen was tested by the example of jellies. The obtained databank broadens information about physico-chemical properties of modified collagen-containing raw materials (cattle rumen)

Rheology and porosity effect on the proliferation of preosteoblast on zirconia ceramics

It has been studied ZrO2(MexOy) based porous ceramics, obtained from the powders consisting of hollow spherical particles. It was shown that the structure is represented as a cellular carcass with a bimodal porosity, formed of a large pore close to a spherical shape and the pores that were not filled with the powder particles during the compaction. For such ceramics the increase of pore volume is accompanied by an increase in strain in an elastic area. It was also shown that the porous ZrO2 ceramics had no acute or chronic cytotoxicity. At the same time, ceramics possess the osteoconductive properties: adhesion support, spreading, proliferation and osteogenic differentiation of MSCs

Relativistic quasiparticle time blocking approximation. Dipole response of open-shell nuclei

The self-consistent Relativistic Quasiparticle Random Phase Approximation (RQRPA) is extended by the quasiparticle-phonon coupling (QPC) model using the Quasiparticle Time Blocking Approximation (QTBA). The method is formulated in terms of the Bethe-Salpeter equation (BSE) in the two-quasiparticle space with an energy-dependent two-quasiparticle residual interaction. This equation is solved either in the basis of Dirac states forming the self-consistent solution of the ground state or in the momentum representation. Pairing correlations are treated within the Bardeen-Cooper-Schrieffer (BCS) model with a monopole-monopole interaction. The same NL3 set of the coupling constants generates the Dirac-Hartree-BCS single-quasiparticle spectrum, the static part of the residual two-quasiparticle interaction and the quasiparticle-phonon coupling amplitudes. A quantitative description of electric dipole excitations in the chain of tin isotopes (Z=50) with the mass numbers A = 100, 106, 114, 116, 120, and 130 and in the chain of isotones with (N=50) 88-Sr, 90-Zr, 92-Mo is performed within this framework. The RQRPA extended by the coupling to collective vibrations generates spectra with a multitude of '2q+phonon' (two quasiparticles plus phonon) states providing a noticeable fragmentation of the giant dipole resonance as well as of the soft dipole mode (pygmy resonance) in the nuclei under investigation. The results obtained for the photo absorption cross sections and for the integrated contributions of the low-lying strength to the calculated dipole spectra agree very well with the available experimental data.Comment: 43 pages, 3 figure

Benchmarking nuclear models for Gamow-Teller response

A comparative study of the nuclear Gamow-Teller response (GTR) within conceptually different state-of-the-art approaches is presented. Three nuclear microscopic models are considered: (i) the recently developed charge-exchange relativistic time blocking approximation (RTBA) based on the covariant density functional theory, (ii) the shell model (SM) with an extended "jj77" model space and (iii) the non-relativistic quasiparticle random-phase approximation (QRPA) with a Brueckner G-matrix effective interaction. We study the physics cases where two or all three of these models can be applied. The Gamow-Teller response functions are calculated for 208-Pb, 132-Sn and 78-Ni within both RTBA and QRPA. The strengths obtained for 208-Pb are compared to data that enables a firm model benchmarking. For the nucleus 132-Sn, also SM calculations are performed within the model space truncated at the level of a particle-hole (ph) coupled to vibration configurations. This allows a consistent comparison to the RTBA where ph+phonon coupling is responsible for the spreading width and considerable quenching of the GTR. Differences between the models and perspectives of their future developments are discussed.Comment: 9 pages, 2 figures, 1 table; to be published in Phys. Lett.