Nuclear Symmetry Energy and the Breaking of the Isospin Symmetry: How Do They Reconcile with Each Other?

We analyze and propose a solution to the apparent inconsistency between our current knowledge of the equation of state of asymmetric nuclear matter, the energy of the isobaric analog state (IAS) in a heavy nucleus such as ^{208}Pb, and the isospin symmetry breaking forces in the nuclear medium. This is achieved by performing state-of-the-art Hartree-Fock plus random phase approximation calculations of the IAS that include all isospin symmetry breaking contributions. To this aim, we propose a new effective interaction that is successful in reproducing the IAS excitation energy without compromising other properties of finite nuclei.

Observation of low- and high-energy Gamow-Teller phonon excitations in nuclei.

Gamow-Teller (GT) transitions in atomic nuclei are sensitive to both nuclear shell structure and effective residual interactions. The nuclear GT excitations were studied for the mass number A = 42, 46, 50, and 54 "f-shell" nuclei in ((3)He, t) charge-exchange reactions. In the (42)Ca → (42)Sc reaction, most of the GT strength is concentrated in the lowest excited state at 0.6 MeV, suggesting the existence of a low-energy GT phonon excitation. As A increases, a high-energy GT phonon excitation develops in the 6-11 MeV region. In the (54)Fe → (54)Co reaction, the high-energy GT phonon excitation mainly carries the GT strength. The existence of these two GT phonon excitations are attributed to the 2 fermionic degrees of freedom in nuclei.

Identification of the ß+ isovector spin monopole resonance via the 208Pb and 90Zr(t,3He) reactions at 300 MeV/u.

The double-differential cross sections for the (208)Pb and (90)Zr(t,(3)He) reactions at 300 MeV/u have been measured at the RI Beam Factory at RIKEN. This was the first physics experiment with the SHARAQ magnetic spectrometer. The combined analysis of the present (t,(3)He) data and previous (n,p) data provides the clearest identification for the ß(+) isovector spin monopole resonance both in the (208)Tl and (90)Y nuclei, and puts the observations of this giant resonance on a firm foundation. The measured distributions of the (t,(3)He) monopole cross sections were well reproduced by the distorted-wave Born approximation calculation, where the target transition density was calculated with the self-consistent Hartree-Fock plus random-phase approximation using the T43 Skyrme interaction. A major part of the expected ß(+) isovector spin monopole strength was found in the measured cross section spectra.

Investigation of irradiation conditions for recurrent breast cancer in JRR-4.

Clinical trials of boron neutron capture therapy (BNCT) for recurrent breast cancers are considered at Japan Research Reactor No. 4 (JRR-4). In this study, the irradiation technique for a total mastectomy patient with recurrent cancer was optimized by dosimetric calculations using JAEA computational dosimetry system (JCDS). The evaluation was performed using an en face technique and a tangents technique with thermal neutron beam mode at JRR-4. The results revealed that equivalent doses of lung, heart, liver and skin were similar in each irradiation technique due to the isotropic scattering of thermal neutrons in the body. On the other hand, the irradiation time with the tangents technique was a few times longer than with the en face technique. We concluded that the en face technique was an optimal irradiation technique for recurrent breast cancers using thermal neutron beam mode in terms of shorter irradiation time and easier patient positioning.

Effect of the tensor force on the charge exchange spin-dipole excitations of 208Pb.

The charge exchange spin-dipole (SD) excitations of 208Pb are studied by using a fully self-consistent Skyrme Hartree-Fock plus random phase approximation formalism which includes the tensor interaction. It is found, for the first time, that the tensor correlations have a unique, multipole-dependent effect on the SD excitations; that is, they produce a softening of 1{-} states, but a hardening of 0{-} and 2{-} states. This paves the way to a clear assessment of the strength of the tensor terms. We compare our results with a recent measurement, showing that our choice of tensor terms improves the agreement with experiment. The robustness of our results is supported by the analytic form of the tensor matrix elements.

Coexistence of BCS- and BEC-like pair structures in halo nuclei.

We investigate the spatial structure of the two-neutron wave function in the Borromean nucleus (11)Li, using a three-body model of (9)Li + n + n, which includes many-body correlations stemming from the Pauli principle. The behavior of the neutron pair at different densities is simulated by calculating the two-neutron wave function at several distances between the core nucleus (9)Li and the center of mass of the two neutrons. With this representation, a strong concentration of the neutron pair on the nuclear surface is for the first time quantitatively established for neutron-rich nuclei. That is, the neutron pair wave function in (11)Li has an oscillatory behavior at normal density, while it becomes a well-localized single peak in the dilute density region around the nuclear surface. We point out that these features qualitatively correspond to the BCS- and BEC-like structures of the pair wave function found in infinite nuclear matter.

Survival and axonal regeneration of off-center retinal ganglion cells of adult cats are promoted with an anti-glaucoma drug, nipradilol, but not BDNF and CNTF.

OFF-center retinal ganglion cells (RGCs) occupy a smaller proportion than ON RGCs when RGCs regenerate axons into a transplanted peripheral nerve. We examined whether the regeneration ability of OFF RGCs in adult cats was promoted when the numbers of regenerating RGCs were increased with brain-derived neurotrophic factor (BDNF)+ciliary neurotrophic factor (CNTF)+forskolin (BCF) or 3,4-dihydro-8-(2-hydroxy-3-isopropylamino)-propoxy-3-nitroxy-2H-1-benzopyran (nipradilol), an anti-glaucoma drug. ON or OFF RGCs were morphologically determined on the basis of their dendritic ramification in the inner plexiform layer using computational analysis. In the normal intact retina the ratio of ON and OFF RGCs (ON/OFF ratio) was 1.25 (55%/44%); whereas, it was 2.61 in regenerating RGCs with saline injection (control) 6 weeks after peripheral nerve transplantation. Estimated numbers of regenerating ON and OFF RGCs were 2149 and 895, respectively. An injection of BCF increased only numbers of ON RGCs into 5766 (2.7-fold to control) but not that of OFF RGCs, n=858. Nipradilol increased both estimated numbers of ON (11,518, 5.4-fold to control) and OFF RGCs (7330, 8.2-fold to control). In the retinas with optic nerve (OpN) transection and intravitreal saline-, BCF- or nipradilol-injection, numbers of ON and OFF RGCs surviving axotomy showed similar trend to that in regenerating RGCs. Thus, nipradilol promoted the survival and regeneration abilities of both of ON and OFF RGCs whereas BCF only did the abilities of ON RGCs. The distribution of tropo-myosin-related kinase B, BDNF receptor, was sparser in the outer two thirds of inner plexiform layer. The lower surviving ability of OFF-RGCs may be attributed in part to the distribution.

Electromagnetic moments of the beta-emitting nucleus 16N.

The nuclear magnetic dipole moment mu and electric quadrupole moment Q of the beta-emitting 16N(Ipi = 2(-), T(1/2) = 7.13 s) nucleus have been determined for the first time by detecting its beta-NMR in a MgO crystal and beta-NQR (nuclear quadrupole resonance) in a TiO (2) crystal to be /mu/ = (1.9859+/-0.0011) mu(N) and /Q/ = (17.9+/-1.7) mb, respectively. Although the prediction of mu given by the Hartree-Fock calculation agrees well with the experiment, an abnormally small effective charge for neutrons is required to account for the experimental Q.

Flow cytometric analysis of leukocytes and reticulocytes stained with proflavine.

Proflavine, an acridine analog for industrial use, was used to stain blood cells. A drop of blood treated with ethylenediaminetetraacetic acid-2K was mixed with a 0.00001% solution of the dye and observed immediately by fluorescence microscopy with a green filter. Leukocytes, platelets, and reticulocytes were stained but mature red blood cells were not. Chromatin in the nuclei of all leukocytes and nucleoli of lymphocytes and monocytes had greenish-yellow fluorescence, and the kind of cell could be identified by the tone and intensity of this color. Granules in granulocytes were in green. Reticular fine-granular or granulofibrous structures in the reticulocytes were brownish. The proflavine could be used routinely in clinical laboratories because this single stain makes possible simultaneous differentiation of leukocytes and counting of reticulocytes.

Molecular-pathological analysis of a patient with three synchronous squamous cell carcinomas in the aerodigestive tract.

A case of synchronous squamous cell carcinomas in the soft palate, larynx and esophagus is reported, along with findings of molecular-pathological analysis. A biopsy sample from the aryngeal carcinoma revealed well differentiated squamous cell carcinoma harboring two point mutations at codons 144 and 148 of the p53 gene but not at codon 299, and more than 50% of the cancer cells showed accumulation of p53 protein immunohistochemically. The esophageal tumor, which was moderately differentiated squamous cell carcinoma, showed immunoreactivity for p53 within the nuclei of 25-50% of cancer cells with a missense mutation at codon 299 but not at codon 144 or 148. This cancer also showed immunoreactivity for transforming growth factor alpha. On the other hand, the poorly differentiated squamous cell carcinoma in the soft palate showed negative immunoreactivity for p53 and no point mutation in exons 5 to 8 of the gene. These results suggest that the three synchronous squamous cell carcinomas arose as independent events.

The immunological activity of a deletion mutant of influenza virus haemagglutinin lacking the globular region.

A deletion mutant of influenza virus haemagglutinin (HA; headless HA) lacking the globular region was expressed in CV-1 cells and detected with a monoclonal antibody, C179, which recognizes a conformational epitope in the middle of the stem region of HA and neutralizes all H1 and H2 subtypes. The cDNA coding for the headless HA was constructed from influenza virus A/Okuda/57 (H2N2), which was also used to select C179. The conformational epitope recognized by C179 was highly stable even after removal of the globular region. The survival rate of mice immunized with the headless HA and challenged with lethal influenza virus A/FM/l/47 (H1N1) was significantly higher than that of the control mice. The headless HA has the potential to induce cross-protection against influenza virus infection.

A tightly regulated expression system in Escherichia coli with SP6 RNA polymerase.

A tightly regulated gene-expression system was developed using SP6 RNA polymerase (RpoSP6). The RpoSp6-encoding gene (rpoSP6) was inserted into a mini-F plasmid (mini-F) and expression was controlled by the lactose promoter (P(lac)) and operator (O(lac)) on the plasmid. Therefore, a controlled expression system for the target genes can easily be constructed in various host strains by co-transformation of the system plasmid pFSP6 with other vector plasmids containing the genes linked to the SP6 promoters (P(SP6)). Using the lac gene linked to P(SP6) as a reporter, we evaluated the regulation of expression in this system in various host strains. Low-level expression of lac was detected in Escherichia coli harboring this expression system when RpoSP6 was uninduced, although very low activities of beta-galactosidase (beta-Gal) were observed which were independent of the presence of pFSP6. This basal level of beta-Gal activity was possibly derived, because the P(SP6) element has very weak activity for E. coli RNA polymerase (Rpo). These results showed that RpoSP6 seemed to be produced at very low levels in uninduced cells. Beta-GAl activity increased about 18-32-fold when the expression of rpoSP6 was induced, as compared with the beta-Gal activity when uninduced. The tight regulation of this system is superior to that of other known systems and it has a considerable advantage for gene expression in E. coli.