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Systematic Study of Survival Probability of Excited Superheavy Nuclei

Cheng-Jun XIA; Bao-Xi SUN; En-Guang ZHAO; Shan-Gui ZHOUSubjects: Physics >> Nuclear Physics

The stability of excited superheavy nuclei (SHN) with 100 Z 134 against neutron emission and fission is investigated by using a statistical model. In particular, a systematic study of the survival probability against fission in the 1n-channel of these SHN is made. In present calculations the neutron separation energies and shell correction energies are consistently taken from the calculated results of the finite range droplet model which predicts an island of stability of SHN around Z = 115 and N = 179. It turns out that this island of stability persists for excited SHN in the sense that the calculated survival probabilities in the 1n-channel of excited SHN at the optimal excitation energy are maximized around Z = 115 and N = 179. This indicates that the survival probability in the 1n-channel is mainly determined by the nuclear shell effects. |

Neutron halo in deformed nuclei from a relativistic Hartree-Bogoliubov model in a Woods-Saxon basis

S G Zhou; J Meng; P Ring; E G ZhaoSubjects: Physics >> Nuclear Physics

Halo phenomenon in deformed nuclei is studied by using a fully self-consistent deformed relativistic Hartree-Bogoliubov model in a spherical Woods-Saxon basis with the proper asymptotic behavior at large distance from the nuclear center. Taking a deformed neutron-rich and weakly bound nucleus 44Mg as an example and by examining contributions of the halo, deformation effects, and large spatial extensions, we show a decoupling of the halo orbitals from the deformation of the core. |

Subjects: Physics >> Nuclear Physics

With the relativistic Coulomb wave function boundary condition, the energies, widths and wave functions of the single proton resonant orbitals for 17Ne are studied by the analytical continuation of the coupling constant (ACCC) approach within the framework of the relativistic mean field (RMF) theory. Pairing correlations and contributions from the single-particle resonant orbitals in the continuum are taken into consideration by the resonant Bardeen-Cooper-Schrieffer (BCS) approach, in which constant pairing strength is used. It can be seen that the fully self-consistent calculations with NL3 and NLSH effective interactions mostly agree with the latest experimental measurements, such as binding energies, matter radii, charge radii and densities. The energy of π2s1/2 orbital is slightly higher than that of π1d5/2 orbital, and the occupation probability of the (π2s1/2)2 orbital is about 20%, which are in accordance with the shell model calculation and three-body model estimation. |

Quantifying the sequence-function relation in gene silencing by bacterial small RNAs

Yue Hao; Zhongge J. Zhang; David W. Erickson; Min Huang; Yingwu Huang; Junbai Li; Terence Hwa; hualin shiSubjects: Physics >> Interdisciplinary Physics and Related Areas of Science and Technology

Sequence-function?relations for?small?RNA (sRNA)-mediated?gene?silencing?were quantified for?the?sRNA RyhB and some of its mRNA targets?in?Escherichia coli. Numerous mutants of RyhB and its targets were generated and their?in?vivo functions characterized at various levels of target and RyhB expression. Although a core complementary region is required for repression?by?RyhB, variations?in?the?complementary sequences of?the?core region gave rise to a continuum of repression strengths, correlated exponentially with?the?computed free energy of RyhB-target duplex formation. Moreover,?sequence?variations?inthe?linker region known to interact with?the?RNA chaperone Hfq also gave rise to a continuum of repression strengths, correlated exponentially with?thecomputed energy cost of keeping?the?linker region open. These results support?the?applicability of?the?thermodynamic model?in?predicting sRNA-mRNA interaction and suggest that sequences at these locations may be used to fine-tune?the?degree of repression. Surprisingly, a truncated RyhB without?the?Hfq-binding region is found to repress multiple targets of?the?wild-type RyhB effectively, both?in?the?presence and absence of Hfq, even though?the?former is required for?the?activity of wild-type RyhB itself. These findings challenge?the?commonly accepted model concerning?the?function?of Hfq?in?gene?silencing-bothin?providing stability to?the?sRNAs and?in?catalyzing?the?target mRNAs to take on active conformations-and raise?the?intriguing question of why many endogenous sRNAs subject their functions to Hfq-dependences. |

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