Density dependence of nuclear symmetry energy constrained by mean-field calculations

We establish a correlation for the symmetry energy at saturation density $S_{0}$, slope parameter $L$ and curvature parameter $K_{\text{sym}}$ based on widely different mean field interactions. With the help of this correlation and available empirical and theoretical information, the density dependent behavior around the saturation density is determined. We compare the results obtained with the present approach with those by other analyses. With this obtained density dependent behavior of the symmetry energy, the neutron skin thickness of $^{208}$Pb and some properties of neutron stars are investigated. In addition, it is found that the expression $S(\rho)=S_{0}(\rho /\rho_{0})^{\gamma}$ or $S(\rho)=12.5(\rho /\rho_{0}) ^{2/3}+C_{p}(\rho /\rho_{0}) ^{\gamma}$ does not reproduce the density dependence of the symmetry energy as predicted by the mean-field approach around nuclear saturation density.Comment: 6 pages, 4 figure

Alpha-decay half-lives and Q_alpha values of superheavy nuclei

The alpha-decay half-lives of recently synthesized superheavy nuclei (SHN) are investigated based on a unified fission model (UFM) where a new method to calculate the assault frequency of alpha-emission is used. The excellent agreement with the experimental data indicates the UFM is a useful tool to investigate these alpha-decays. It is found that the half-lives become more and more insensitive to the Q_alpha values as the atomic number increases on the whole, which is favorable for us to predict the half-lives of SHN. In addition, a formula is suggested to compute the Q_alpha values for the nuclei with Z > 92 and N > 140 with a good accuracy, according to which the long-lived SHN should be neutron rich. With Q_alpha values from this formula as inputs, we predict the half-lives of isotopes of Z = 117, which may be useful for experimental identication in the future.Comment: 7 pages, 3 figure

Significant changes in subseries means and variances in an 8000-year precipitation reconstruction from tree rings in the southwestern USA

Both algorithms were applied to an 8000-year long time series of annual precipitation that was reconstructed from tree rings in the southwestern USA. One of the algorithms is the scanning <I>t</I>-test, which detects significant changes in subseries means (the first center moments) on various time scales. Another is the scanning <I>F</I>-test, which detects significant changes in subseries variances (the second center moments) on multi-time scales. Firstly, the scanning <I>t</I>-test identified 22 change points in subseries means and partitioned the series into 23 relatively wet, normal or dry episodes. Secondly, the scanning <I>F</I>-test detected 15 change points in subseries variances and divided 16 phases in comparatively steady (with smaller variance) or unsteady (with larger variance) features. Thirdly, the 23 wetness-episodes were characterized as the steady or unsteady situations by jointing the results from the scanning <I>F</I>-test into those from the <I>t</I>-test. Fourthly, the 23 episodes were compared to those in the TIC and δ<sup>18</sup>O records from cored sediments in the deep basin of the Pyramid Lake in Nevada by using a coherency analysis of the <I>t</I>-test between the precipitation reconstruction and the TIC or δ<sup>18</sup>O series. Fifthly, the 23 episodes were collaborated with some published papers in related studies. In addition, the 23 episodes were also compared with studies of the global climate change and with documents of climate changes in China during the same periods. As the TIC and δ<sup>18</sup>O record series are high resolution with unequal sampling intervals between 3 and 14 years, an algorithm in the scanning <I>t</I>-test for dealing with the unequal time intervals was developed in this study