25,422 research outputs found
Dynamic Pairing Effects on Low-Frequency Modes of Excitation in Deformed Mg Isotopes close to the Neutron Drip Line
Low-frequency quadrupole vibrations in deformed Mg are studied
by means of the deformed Quasiparticle-RPA based on the coordinate-space
Hartree-Fock-Bogoliubov formalism. Strongly collective and
excitation modes (carrying 10-20 W.u.) are obtained at about 3 MeV. It
is found that dynamical pairing effects play an essential role in generating
these modes. It implies that the lowest excitation modes are
particularly sensitive indicators of dynamical pairing correlations in deformed
nuclei near the neutron drip line.Comment: Talk given at Int. Conference "Finite Fermionic Systems: Nilsson
Model 50 Years", Lund, Sweden, June 14-18, 200
Charge-exchange dipole excitations in neutron-rich nuclei: , anti-analog pygmy, and anti-analog giant resonances
The occurrence of the low-lying charge-exchange non spin-flip dipole modes
below the giant resonance in neutron-rich nuclei is predicted on the basis of
nuclear density functional theory. The ground and excited states are described
in the framework of the self-consistent Hartree-Fock-Bogoliubov and the
proton-neutron quasiparticle-random-phase approximation employing a Skyrme-type
energy density functional. The model calculations are performed for the
spherical neutron-rich Ca, Ni, and Sn isotopes. It is found that the low-lying
states appear sensitively to the shell structure associated with the excitation below the Gamow-Teller states. Furthermore, the pygmy
resonance emerges below the giant resonance when the neutrons occupy the
low- orbitals analogous to the pygmy resonance seen in
the electric dipole response.Comment: 5 pages, 5 figure
Studies on reticuloendothelial system and hemato-poiesis, III. Relationship between differentiation of erythroblast and oxygen tension
For the purpose to clarify the control mechanism of erythroid cell differentiation, the author observed morphologic changes in bone-marrow cells and circulating
red cells in phenylhydrazine anemia of rabbits by introducing a mass of red cells into vein at one time and reached the following conclusions. 1. After red cell transfusion in a mass to animal showing a marked hematopoietic activity, anisocytosis or macrocytosis becomes distinct with the appearance of big reticulocytes and red cells as large as four times the normal in
volume. This suggests, judging from their volume, the accelerated denucleation of erythroblast as early as at the late basophilic stage. 2. Observations on bone marrow at this stage revealed the reduction in the number of erythroblasts of undifferentiated type with the increase of rather differentiated ones. In erythroid islet, undifferentiated cells are found surrounding
a reticulum cell located in the center, while well differentiated ones in the outskirt area are situated near the sinusoid. Such a cell arrangement suggests that the erythroid cell requires a high oxygen tension for its differentiation. 3. From these observations and other results obtained from the studies on reticulocyte maturation and RNA synthesis of erythroblast, the author stresses that erythroid cells can differentiate as long as it is provided with a certain level of oxygen, even though it may develop m-RNA for differentiation. In other words, there should be two steps in the differentiation of erythroblast, the first is m-RNA synthesis induced by the information and the second is the somatic
protein synthesis with oxygen supply. This seems to be directly connected to the control mechanism of hematopoiesis by oxygen.</p
Suddenly shortened half-lives beyond Ni: magic number and high-energy non-unique first-forbidden transitions
-decay rates play a decisive role in understanding the nucleosynthesis
of heavy elements and are governed by microscopic nuclear-structure
information. A sudden shortening of the half-lives of Ni isotopes beyond
was observed at the RIKEN-RIBF. This is considered due to the persistence of
the neutron magic number in the very neutron-rich Ni isotopes. By
systematically studying the -decay rates and strength distributions in
the neutron-rich Ni isotopes around , I try to understand the microscopic
mechanism for the observed sudden shortening of the half-lives. The
-strength distributions in the neutron-rich nuclei are described in the
framework of nuclear density-functional theory. I employ the Skyrme
energy-density functionals (EDF) in the Hartree-Fock-Bogoliubov calculation for
the ground states and in the proton-neutron Quasiparticle Random-Phase
Approximation (pnQRPA) for the transitions. Not only the allowed but the
first-forbidden (FF) transitions are considered. The experimentally observed
sudden shortening of the half-lives beyond is reproduced well by the
calculations employing the Skyrme SkM* and SLy4 functionals. The sudden
shortening of the half-lives is due to the shell gap at and
cooperatively with the high-energy transitions to the low-lying and
states in the daughter nuclei. The onset of FF transitions pointed out around
and 126 is preserved in the lower-mass nuclei around . This study
suggests that needed is a microscopic calculation where the shell structure in
neutron-rich nuclei and its associated effects on the FF transitions are
selfconsistenly taken into account for predicting -decay rates of exotic
nuclei in unknown region.Comment: 8 pages, 7 figures and 1 tabl
Identification and Estimation of Partial Effects with Proxy Variables
I develop a new identification approach for partial effects in nonseparable
models with endogeneity. I use a proxy variable for the unobserved
heterogeneity correlated with the endogenous variable to construct a valid
control function, where the definition of a proxy variable is the same as in
the measurement error literature. The identifying assumptions are distinct from
existing methods, in particular instrumental variables and selection on
observables approaches, and I provide an alternative identification strategy in
settings where existing approaches are not applicable. Building on the
identification result, I consider three estimation approaches, ranging from
nonparametric to flexible parametric methods, and characterize asymptotic
properties of the proposed estimators.Comment: 48 pages with the appendi
Studies on reticuloendothelial system and hemaotpoiesis. I. Studies of extramedullary hematopoiesis
The author studied the hematopoietic disturbances of rabbit induced by saponin injection and drew the following conclusions: 1) By saponin injection, the structure of bone marrow is disintegrated and hematopoietic cells are released into the circulating blood forming extramedullary
hematopietic foci mainly in liver and spleen. The main attacking point of saponin should be RES. Recovery of hematopoietic foci is associated with the recovery of RES. The most marked extramedullary hematopoiesis is found three days after the injection. Thereafter, bone-marrow hematopoiesis proceeds to recovery stage, during which hematopoietic foci in liver and spleen are preserved, especially those in spleen persist fairly for a long time.
2) Daily injections of India ink kept up over a long period of time after the treatment with saponin, prevent the recovery of anemia and bone-marrow hematopoiesis. The lymph nodes, whose RES escaped from the severe damage
by India ink, keep the hematopoietic foci for a long time.
3) As far as hematopoiesis is concerned, there seems to be no functional differentiation among RE cells, though they seem to have a special function according to the organs to which they belong, e. g. antibody formation in lymph
apparatus, hematopoiesis in bone marrow and red cell destruction in spleen.</p
- …