349 research outputs found
Altered expression of microRNA-451 in eutopic endometrium of baboons ( Papio anubis ) with endometriosis
Are microRNAs (miRs) altered in the eutopic endometrium (EuE) of baboons following the induction of endometriosis
Rotation-aligned isomer and oblate collectivity in Pt 196
An oblate rotational sequence, built on an aligned, two-quasineutron isomeric state has been established in Pt196. The isomer has a half-life of 7.7(7) ns and is associated with the IÏ€=12+,(i13/2)2 neutron configuration. Excited states, with angular momentum generated primarily through successive nucleon alignments, have been populated through 1p transfer from Au197. The nucleus Pt196 is the most neutron-rich Pt isotope for which high-spin states, beyond the 12+ isomeric state, have been established thus far. Cranked shell model calculations have been performed to understand shape evolution with spin, and the role of nucleons occupying specific Nilsson orbitals in generating aligned angular momentum for both prolate and oblate deformations has been explored
Isomers and oblate rotation in Pt isotopes: Delineating the limit for collectivity at high spins
Rotation-aligned isomeric states and associated oblate collective sequences are established in even Pt isotopes. Reduced E2 transition probabilities for the deexcitation of the 12+ isomers indicate an abrupt and unexpected quenching of oblate collectivity around neutron number N=120. Structure and shape evolution at high spin in the heaviest stable isotopes is found to be markedly different from observations in the lighter ones
Decoupled and semi-decoupled bands in Hg 197 and Hg 199
The structure of decoupled positive-parity and semidecoupled negative-parity bands up to high spin in Hg197,199 has been studied using multinucleon transfer reactions with the Gammasphere array. A positive-parity band in Hg199 with the (νi13/2)3 decoupled configuration that deexcites to levels in the negative-parity sequences is newly established. The semidecoupled sequences in both isotopes are extended to higher spin. Rotation-aligned angular momenta and crossing frequencies determined from experiment are in fair agreement with those from cranking calculations. A transition from oblate collective rotation at low spin to triaxial noncollective shapes at high spin is indicated
High-K isomers and rotational structures in W174
High-spin states in W174 (Z = 74) have been populated using the reaction Te128(Ti50, 4n)W174 at beam energies of 215 and 225 MeV. The Gammasphere array was used to detect the γ rays emitted by the evaporation residues. Four previously known collective band structures have been extended, and 16 new rotational sequences observed. Two are built upon isomeric states, one corresponding to a two-quasiparticle K = 8 isomer, the other to a four-quasiparticle K = 12 isomer, with the latter exhibiting strong K-violating ΔK=12 decays to the ground state band. Nucleonic configurations for the two- and four-quasiparticle excitations are proposed, and Woods-Saxon cranking calculations are presented to understand the rotational structures. Decay mechanisms of multi-quasiparticle K isomers are discussed in terms of the prevalent phenomenological models, with special emphasis on γ-tunneling calculations. Surprisingly, the latter underpredict the decay hindrance for the K = 12 isomer by three orders of magnitude, unlike all other isomer decays in this mass region
Collective oblate rotation at high spins in neutron-rich Hf180
We report on experimental evidence for collective oblate rotation becoming favored at high spins in a rigid, well-deformed, axially symmetric nucleus. Excited states established up to spin 20 in Hf180 are consistent with predictions that nucleon alignments would favor oblate over prolate shapes at high spins in neutron-rich Hf isotopes. The results highlight the influence of valence orbitals on the interplay between nucleon alignments and nuclear shapes and provide a rare example of independent particle dynamics in competing potential wells
Isomers from intrinsic excitations in Tl 200 and Pb 201,202
A six-quasiparticle isomer with T1/2 = 57(2) ns has been established in the doubly-odd isotope Tl200 and its level scheme is significantly extended. Half-lives of previously reported isomers in Tl200 and Pb201,202 have been determined and revised values are reported in a few cases, with T1/2 = 397(17) ns and 7.0(5) ns for the IÏ€=5+ and 7- states in Tl200, 52(2) ns for the 41/2+ level in Pb201, and 93(4) ns for the 16+ state in Pb202. Configurations for the isomers have been assigned and these predominantly involve intrinsic excitations of neutrons from the i13/2 subshell. The inferred transition rates for the decay of these isomers compare well with single-particle estimates attesting to their intrinsic character
Structure of odd- A Pt isotopes along the line of stability
The structure of the odd-A isotopes Pt193,195,197, which lie along the line of stability, has been studied up to high spin through multinucleon transfer reactions. Positive- and negative-parity sequences in Pt193,195 have been considerably extended and multiple band crossings established. An isomer with T1/2=5.0(5) ns and IÏ€=25/2- is present in Pt195. The isotopes Pt193,195 are characterized by moderate oblate deformation, and angular momentum generation at high spin in the yrast, positive-parity sequences is attributed to the rotation alignment of i13/2 neutrons and h11/2 protons. A detailed understanding of the observed features is presented using calculations based on tilted axis cranking covariant density functional theory as well as others with the ultimate cranker code
Nanosecond isomers and the evolution of collectivity in stable, even-A Hg isotopes
Isomeric states and associated collective structures have been studied up to high spin in Hg198,200,202 using multinucleon transfer reactions and the Gammasphere array. A coupled rotational band, with possible four-quasiparticle character, is established in Hg198. Sequences built on two-quasiparticle, positive-and negative-parity levels are assigned to Hg202. New isomers in Hg202 with IÏ€=(7-) and (9-), and T1/2 = 10.4(4) ns and 1.4(3) ns, respectively, have been identified. A half-life of 1.0(3) ns is established for the IÏ€=12+ state in Hg200. B(E2) values deduced from isomeric transitions in Hg isotopes indicate that, while collectivity near the ground state gradually diminishes from N = 112 to N = 124, it is found to increase for the 12+ and 9-states up to N = 118, followed by a reduction for higher neutron numbers. Calculations using the ultimate cranker code provide insight into the variation of deformation with spin and allow for an understanding of observed band crossings. The evolution of collectivity with spin, and along the isotopic chain, is described
Decay spectroscopy of two-quasiparticle K isomers in Cm 246,248 via inelastic and transfer reactions
The decay of K isomers in Cm (Z = 96) isotopes has been studied using inelastic and transfer reactions. The half-life of a previously identified 2-quasiparticle (qp) Kπ=8- isomer in Cm246 has been measured. A new 2-qp isomer is observed in Cm248, its half-life measured and its decay scheme established. The reduced K hindrances extracted for the decay transitions from the isomers in Cm246,248 indicate K to be a robust quantum number and validate axial symmetry in these nuclei. The excitation energies of the 2-qp isomers in Cm246 (N = 150) and Cm248 (N = 152) support the persistence of a deformed subshell gap at N = 152 in the Z≈100 region down to Z = 96 nuclei
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