Adopted values for the reduced electric quadrupole transition probability, B(E2)↑, from the ground state to the first-excited 2+ state of even–even nuclides are given in Table I. Values of τ, the mean life of the 2+ state; E, the energy; and β, the quadrupole deformation parameter, are also listed there. The ratio of β to the value expected from the single-particle model is presented. The intrinsic quadrupole moment, Q0, is deduced from the B(E2)↑ value. The product E×B(E2)↑ is expressed as a percentage of the energy-weighted total and isoscalar E2 sum-rule strengths.

Table II presents the data on which Table I is based, namely the experimental results for B(E2)↑ values with quoted uncertainties. Information is also given on the quantity measured and the method used. The literature has been covered to November 2000.

The adopted B(E2)↑ values are compared in Table III with the values given by systematics and by various theoretical models. Predictions of unmeasured B(E2)↑ values are also given in Table III.

Transition probability from the ground to the first-excited 2^+ state of even-even nuclides

Fusion and breakup of weakly bound nuclei

We describe a sequential (step by step) Darwinian model for the evolution of life from the late stages of the RNA world through to the emergence of eukaryotes and prokaryotes. The starting point is our model, derived from current RNA activity, of the RNA world just prior to the advent of genetically-encoded protein synthesis. By focusing on the function of the protoribosome we develop a plausible model for the evolution of a protein-synthesizing ribosome from a high-fidelity RNA polymerase that incorporated triplets of oligonucleotides. With the standard assumption that during the evolution of enzymatic activity, catalysis is transferred from RNA → RNP → protein, the first proteins in the ``breakthrough organism'' (the first to have encoded protein synthesis) would be nonspecific chaperone-like proteins rather than catalytic. Moreover, because some RNA molecules that pre-date protein synthesis under this model now occur as introns in some of the very earliest proteins, the model predicts these particular introns are older than the exons surrounding them, the ``introns-first'' theory. Many features of the model for the genome organization in the final RNA world ribo-organism are more prevalent in the eukaryotic genome and we suggest that the prokaryotic genome organization (a single, circular genome with one center of replication) was derived from a ``eukaryotic-like'' genome organization (a fragmented linear genome with multiple centers of replication). The steps from the proposed ribo-organism RNA genome → eukaryotic-like DNA genome → prokaryotic-like DNA genome are all relatively straightforward, whereas the transition prokaryotic-like genome → eukaryotic-like genome appears impossible under a Darwinian mechanism of evolution, given the assumption of the transition RNA → RNP → protein. A likely molecular mechanism, ``plasmid transfer,'' is available for the origin of prokaryotic-type genomes from an eukaryotic-like architecture. Under this model prokaryotes are considered specialized and derived with reduced dependence on ssRNA biochemistry. A functional explanation is that prokaryote ancestors underwent selection for thermophily (high temperature) and/or for rapid reproduction (r selection) at least once in their history.

/pdf/the-path-from-the-rna-world-bsie3bxa1v.pdf

The path from the RNA world.

Quantum groups and their applications in nuclear physics

Recent developments in fusion and direct reactions with weakly bound nuclei

Magnetic moments of even rare-earth nuclei in the cranked HFB approach

Oblate bands in doubly odd 134la

A phenomenological description of the ground state band energies of even-even nuclei, based on an anharmonic vibrational picture, is developed. The proposed model, with three adjustable parameters, gives excellent fits to the experimental spectra in the spherical, transitional, and deformed regions.

Phenomenological anharmonic vibrator model for ground state bands of even-even nuclei

Excited states of 68Ga have been investigated through the 55Mn(16O, 2pn) reaction at projectile energy 55 MeV. The level scheme has been extended up to 7.8 MeV. Altogether six new excited levels could be identified and twelve previously unobserved γ-transitions have been placed in the modified level scheme.

Level structure of odd-odd 68 Ga

The particle-rotor model has been applied to calculate the band structure in a number of highly neutron deficient odd-{ital A} rare-earth nuclei in the {ital A}{congruent}130--150 region. Several transitional nuclei are also included in the study. The only adjustable parameter, used in the calculation, is the Coriolis attenuation coefficient. However, it is seen that the observed band structures in these nuclei can be reproduced practically without any {ital ad} {ital hoc} reduction of the Coriolis matrix elements. The systematics of the Coriolis attenuation in the neutron-deficient, transitional, and well-deformed rare-earth nuclei are discussed in the light of the present work and several theoretical studies, made earlier. The importance of the pairing interaction in the Coriolis attenuation study is emphasized.

S. Sen

Papers

Magnetic moments of even rare-earth nuclei in the cranked HFB approach

Oblate bands in doubly odd 134la

Phenomenological anharmonic vibrator model for ground state bands of even-even nuclei

Level structure of odd-odd 68 Ga

Coriolis attenuation in the A