Nuclear descent from the fission barrier in the presence of long--range memory effects

We have investigated the peculiarities of nuclear descent from a parabolic fission barrier within a generalized Langevin equation with power--law $f(t-t')=(|t-t'|/\tau)^{-\alpha}$ memory function. We have observed much stronger slowing down of the nuclear descent in the presence of long--range memory effects, caused by the power--law memory function at $0<\alpha<1$, than in the presence of short--range memory effects, generated by exponential $f(t-t')={\rm exp}(-|t-t'|/\tau)$ memory function. At a specific value of the exponent $\alpha=1/2$ of the power--law memory function, it turned out possible to find analytically the trajectory of the descent and demonstrate that the long--range memory effects give rise to complex time oscillations of nuclear shape, becoming more frequent and damped with the correlation time $\tau$. We have found fairly long ($>10^{-20}~{\rm s}$) times of the descent of $^{\rm 236}{\rm U}$ at the values of the correlation time $\tau \sim [10^{-24}\div 10^{-23}]~{\rm s}$

A simple approach to the chaos-order contributions in nuclear spectra

The simple one-parameter nearest neighbor-spacing distribution (NNSD) is suggested for statistical analysis of nuclear spectra. This distribution is derived within the Wigner-Dyson approach in the linear approximation for the level repulsion density of quantum states. The obtained NNSD gives the individual information on the Wigner and Poisson contributions in agreement with that of the statistical experimental distributions of collective states in deformed nuclei. Using this NNSD, one finds that the symmetry breaking due to the fixing of projections of the angular momentum of collective states enhances a chaos as a shift of the NNSD from the Poisson to Wigner distribution behavior.Comment: 6 pages, 3 figures. arXiv admin note: text overlap with arXiv:1711.0184

Получение материалов на основе сополимера лактида и гликолида для восстановления кровеносных сосудов

В ходе эксперимента были получены пленки сополимера лактида и гликолида с различными характеристиками поверхности. С использованием методов сканирующей электронной микроскопии и профилометрии, а также методов ИК-спектроскопии установлен состав, структура и морфология поверхности полученных полимерных пленок. Показано образование различных агрегатов на поверхности пленок в зависимости от способа обработки материала. Установлено, что при получении пленок они частично подвергаются гидролизу, а шероховатость образцов зависит от способа обработки

Collective motion in quantum diffusive environment

The general problem of dissipation in macroscopic large-amplitude collective motion and its relation to energy diffusion of intrinsic degrees of freedom of a nucleus is studied. By applying the cranking approach to the nuclear many-body system, a set of coupled dynamical equations for the collective classical variable and the quantum mechanical occupancies of the intrinsic nuclear states is derived. Different dynamical regimes of the intrinsic nuclear motion and its consequences on time properties of collective dissipation are discussed.Comment: 15 pages, 5 figure