616 research outputs found
Why does the recently proposed simple empirical formula for the lowest excitation energies work so well?
It has recently been shown that a simple empirical formula, in terms of the
mass number and the valence nucleon numbers, is able to describe the main
trends of the lowest excitation energies of the natural parity even multipole
states up to in even-even nuclei throughout the entire periodic table.
In an effort to understand why such a simple formula is so capable, we
investigate the possibility of associating each term of the empirical formula
with the specific part of the measured excitation energy graph.Comment: 9 pages, 3 figure
Spin-dependent empirical formula for the lowest excitation energies of the natural parity states in even-even nuclei
We present an empirical expression which holds for the lowest excitation
energy of the natural parity states in even-even nuclei throughout the entire
periodic table. This formula contains spin-dependent factors so that it is
applied to different multipole states with the same model parameters in
contrast to the recently proposed empirical expression where the model
parameters had to be fitted for each multipole separately.Comment: 9 pages, 5 figure
scheme and the valence proton-neutron interaction
We examine the common belief that the scheme is manifested as a
direct consequence of the valence proton-neutron interaction which has proven
to be a dominant factor in developing collectivity in nuclei. We show that the
simplification of the -plot of the lowest excitation energy is
introduced merely because the excitation energy always decreases when the
valence nucleon number becomes larger.Comment: 10 pages, 6 figure
N_pN_n dependence of empirical formula for the lowest excitation energy of the 2^+ states in even-even nuclei
We examine the effects of the additional term of the type on the recently proposed empirical formula for the lowest excitation
energy of the states in even-even nuclei. This study is motivated by the
fact that this term carries the favorable dependence of the valence nucleon
numbers dictated by the scheme. We show explicitly that there is not
any improvement in reproducing by including the extra
term. However, our study also reveals that the excitation energies
, when calculated by the term alone (with the mass number
dependent term), are quite comparable to those calculated by the original
empirical formula.Comment: 14 pages, 5 figure
Empirical formula applied to the lowest excitation energies of the natural parity odd multipole states in even-even nuclei
We applied our recently proposed empirical formula, a formula quite
successful in describing essential trends of the lowest excitation energies of
the natural parity even multipole states, to the lowest excitation energies of
the natural parity odd multipole states in even-even nuclei throughout the
entire periodic table. Even though the systematic behavior of the lowest
excitation energies of odd multipole states is quite different from those of
even multipole states, we have shown that the same empirical formula also holds
reasonably well for the odd multipole states with the exception of a few
certain instances.Comment: 23 pages, 11 figure
Vav1 inhibits RANKL-induced osteoclast differentiation and bone resorption
Vav1 is a Rho/Rac guanine nucleotide exchange factor primarily expressed in hematopoietic cells. In this study, we investigated the potential role of Vav1 in osteoclast (OC) differentiation by comparing the ability of bone marrow mononuclear cells (BMMCs) obtained from Vav1-deficient (Vav1−/−) and wild-type (WT) mice to differentiate into mature OCs upon stimulation with macrophage colony stimulating factor and receptor activator of nuclear kappa B ligand in vitro. Our results suggested that Vav1 deficiency promoted the differentiation of BMMCs into OCs, as indicated by the increased expression of tartrate-resistant acid phosphatase, cathepsin K, and calcitonin receptor. Therefore, Vav1 may play a negative role in OC differentiation. This hypothesis was supported by the observation of more OCs in the femurs of Vav1−/− mice than in WT mice. Furthermore, the bone status of Vav1−/− mice was analyzed in situ and the femurs of Vav1−/− mice appeared abnormal, with poor bone density and fewer number of trabeculae. In addition, Vav1-deficient OCs showed stronger adhesion to vitronectin, an αvβ3 integrin ligand important in bone resorption. Thus, Vav1 may inhibit OC differentiation and protect against bone resorption
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