41 research outputs found
Isospin-symmetry breaking in superallowed Fermi beta-decay due to isospin-nonconserving forces
We investigate isospin-symmetry breaking effects in the sd-shell region with
large-scale shell-model calculations, aiming to understand the recent anomalies
observed in superallowed Fermi beta-decay. We begin with calculations of
Coulomb displacement energies (CDE's) and triplet displacement energies (TDE's)
by adding the T=1,J=0 isospin nonconserving (INC) interaction into the usual
isospin-invariant Hamiltonian. It is found that CDE's and TDE's can be
systematically described with high accuracy. A total number of 122 one- and
two-proton separation energies are predicted accordingly, and locations of the
proton drip-line and candidates for proton-emitters are thereby suggested.
However, attempt to explain the anomalies in the superallowed Fermi beta-decay
fails because these well-fitted T=1,J=0 INC interactions are found no effects
on the nuclear matrix elements. It is demonstrated that the observed large
isospin-breaking correction in the 32Cl beta-decay, the large isospin-mixing in
the 31Cl beta-decay, and the small isospin-mixing in the 23Al beta-decay can be
consistently understood by introducing additional T=1,J=2 INC interactions
related to the s1/2 orbit.Comment: 7 pages, 3 figures, accepted in Phys. Lett.
Systematic study of high-K isomers in the midshell Gd and Dy nuclei
High-K isomers are well known in the rare-earth region and provide unique
access to the high spin structures of the nuclei. With the current interest in
the study of neutron-rich rare-earth nuclei at Radioactive Ion Beam (RIB)
facilities, we present here theoretical results of the band structures of
neutron-rich Gd and Dy nuclei, including the high K-isomers. Apart from the
already known K-isomers, we predict some more K-isomers and these are suggested
for future studies at RIB facilities. Self-consistent Deformed Hartree-Fock and
Angular Momentum Projection theories are used to get the intrinsic structures,
band-spectra and electromagnetic transitions probabilities of the ground band
as well as bands based on isomers.Comment: 10 pages, updated text
Large mirror asymmetry in Gamow-Teller β-decay in the A = 26 isobaric multiplet
We investigate a striking example of mirror asymmetry in Gamow-Teller (GT) β-decay using the nuclear shell-model including isospin-nonconserving (INC) forces in the sd-shell region. We show that the large mirror asymmetry between 26 P and 26 Na GT β-decay can be accurately reproduced by introducing T=1, J≠0 INC forces related to the s 1/2 orbit, while the usual J=0 INC force, commonly adopted to describe isospin-symmetry breaking, does not work. We further show that the calculated distribution of summed GT strength for the 26 P β-decay is in good agreement with the experimental data. Our results support the conclusion that 26 P is a nucleus with proton-halo structure
Preliminary study of feasibility of an experiment looking for excited state double beta transitions in tin
An attempt to study the feasibility of a new experiment to search for double
beta decay in Sn and Sn was carried out by using ultra-low
background HPGe detector (244 cm) inside the Gran Sasso National
Laboratory (LNGS) of the INFN (Italy). A small sample of natural Sn was
examined for 2367.5 h. The radioactive contamination of the sample has been
estimated. The data has also been considered to calculate the present
sensitivity for the proposed search; half-life limits years for EC and EC-EC processes in Sn and
years for transition in Sn were
measured. In the last section of the paper the enhancement of the sensitivity
for a proposed experiment with larger mass to reach theoretically estimated
values of half-lives is discussed.Comment: 20 pages, 11 figures, 4 tables, accepted for publication in NIMA (in
press
Rotational Bands and Electromagnetic Transitions of some even-even Neodymium Nuclei in J-Projected Hartree-Fock Model
Rotational structures of even-even Nd nuclei are studied with the
self-consistent deformed Hartree-Fock (HF) and angular momentum (J) projection
model. Spectra of ground band, recently observed , and a few
more excited, positive and negative parity bands have been studied upto high
spin values. Apart from these detailed electromagnetic properties (like E2, M1
matrix elements) of all the bands have been obtained. There is substantial
agreement between our model calculations and available experimental data.
Predictions are made about the band structures and electromagnetic properties
of these nuclei. Some 4-qasiparticle K-isomeric bands and their electromagnetic
properties are predicted.Comment: 20 page
Differentiation of <i>Staphylococcus aureus</i> strains based on 16S-23S ribosomal RNA intergenic space polymorphism
276-279Discrimination of Staphylococcus aureus strains, isolated from camel abscesses and mastitic milk of camel, cattle and goats, on the basis of 16S-23S ribosomal RNA intergenic space polymorphism was carried out. Two sets of primers were used for amplification of DNA of intergenic space; the one having a highly conserved sequence in eubacterial 23S rRNA transcript, while the other having less conserved sequence of 16S rRNA, reported earlier by other workers. Of the two sets of primers used, amplification could be achieved with one set of primers. Of 60 strains of S. aureus tested, amplification could be achieved in only 18 strains. In these strains the most frequent bands of DNA were of 350, 500, 750 and 1500 base pairs. Polymorphism was noted in the number of the rRNA transcripts and size of the 16S-23S rRNA intergenic space, as evident by variable band pattern in different strains of S. aureus
Kinetics and Mechanism of Reduction of Iron Ore-Coal Composite Pellets and Its Usage in Smelting Reduction Process
Enormous amount of fines are generated in Indian iron ore and coal mines due to mechanized mining and mineral dressing operations. Utilization of these fines for extracting metal is of vital concern for judicious resource utilization and pollution control. The term composite pellet is being employed here to mean a pellet containing mixture of fines of iron bearing oxides and carbonaceous materials (coal/coke/char), which has been imparted sufficient green strength for subsequent handling by cold bonding technique. The reduction kinetics, in iron ore-coal composite pellet, is expected to be enhanced due to the presence of reductant in-situ which causes shortening of diffusion distances of reductant and availability of large number of reaction sites. The reduction kinetics in iron ore-coal composite pellets is very complex with respect to simultaneous reaction steps in a system consisting of solid and gas phases. The movements of reactants and products at the interface are affected by several factors which control the rate of reduction. In iron ore reduction, majority of actual systems involve non-isothermal conditions. The physical properties of the composite pellets have also been evaluated. Composite pellet based alternative ironmaking processes constitute a promising route for ironmaking in future and therefore, a clear understanding of kinetics and mechanism of reduction in composite pellets is extremely important. This paper presents the kinetics and mechanism of reduction of iron oxides in composite pellets under non-isothermal conditions and their usage in smelting reduction processes