Biomedical subjects
Publications and source records attributed to K Yoneda.
Excited states in (40)Si have been established by detecting gamma rays coincident with inelastic scattering and nucleon removal reactions on a liquid hydrogen target. The low excitation energy, 986(5) keV, of the 2(1)(+) state provides evidence of a weakening in the N=28 shell closure in a neutron-rich nucleus devoid of deformation-driving proton collectivity.
An exclusive measurement has been made of the Coulomb dissociation of the two-neutron halo nucleus 11Li at 70 MeV/nucleon at RIKEN. Strong low-energy (soft) E1 excitation is observed, peaked at about Ex = 0.6 MeV with B(E1) = 1.42(18) e2fm2 for Erel < or = 3 MeV, which was largely missed in previous measurements. This excitation represents the strongest E1 transition ever observed at such low excitation energies. The spectrum is reproduced well by a three-body model with a strong two-neutron correlation, which is further supported by the E1 non-energy-weighted cluster sum rule.
This Letter reports on the (1)H((28)Ne, (28)Ne) and (1)H((28)Ne, (27)Ne) reactions studied at intermediate energy using a liquid hydrogen target. From the cross section populating the first 2(+) excited state of (28)Ne, and using the previously determined BE(2) value, the neutron quadrupole transition matrix element has been calculated to be M(n)=13.8 +/- 3.7 fm(2). In the neutron knockout reaction, two low-lying excited states were populated in (27)Ne. Only one of them can be interpreted by the sd shell model while the additional state may intrude from the fp shell. These experimental observations are consistent with the presence of fp shell configurations at low excitation energy in (27,28)Ne nuclei caused by a vanishing N=20 shell gap at Z=10.
The shell structure underlying shape changes in neutron-rich nuclei near N = 28 has been investigated by a novel application of the transient-field technique to measure the first-excited-state g factors in 38S and 40S produced as fast radioactive beams. There is a fine balance between proton and neutron contributions to the magnetic moments in both nuclei. The g factor of deformed 40S does not resemble that of a conventional collective nucleus because spin contributions are more important than usual.
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We report on the first determination of the absolute B(E2;0+(1)-->2+(1)) excitation strength in the N=Z nucleus 72Kr. 72Kr is the heaviest N=Z nucleus for which this quantity has been measured and provides a benchmark in a region of the nuclear chart dominated by rapidly changing deformations and shapes mediated by the interplay of strongly oblate and prolate-driving orbitals. The deduced quadrupole deformation strength is in agreement with a variety of self-consistent models that predict an oblate shape for the ground state of 72Kr. Large-scale shell-model Monte Carlo calculations reproduce the experimental B(E2) value and link the result to the occupation of the deformation-driving g9/2 orbit.
Nuclear shell structures--the distribution of the quantum states of individual protons and neutrons--provide one of our most important guides for understanding the stability of atomic nuclei. Nuclei with 'magic numbers' of protons and/or neutrons (corresponding to closed shells of strongly bound nucleons) are particularly stable. Whether the major shell closures and magic numbers change in very neutron-rich nuclei (potentially causing shape deformations) is a fundamental, and at present open, question. A unique opportunity to study these shell effects is offered by the 42Si nucleus, which has 28 neutrons--a magic number in stable nuclei--and 14 protons. This nucleus has a 12-neutron excess over the heaviest stable silicon nuclide, and has only one neutron fewer than the heaviest silicon nuclide observed so far. Here we report measurements of 42Si and two neighbouring nuclei using a technique involving one- and two-nucleon knockout from beams of exotic nuclei. We present strong evidence for a well-developed proton subshell closure at Z = 14 (14 protons), the near degeneracy of two different (s(1/2) and d(3/2)) proton orbits in the vicinity of 42Si, and a nearly spherical shape for 42Si.
Wild jungle crows (Corvus macrorhynchos) captured from three different areas of Tokyo were examined to evaluate environmental contamination of dioxins. In addition to the pathologic examination of their whole body, accumulation of dioxins, mRNA expression of the aryl hydrocarbon receptor (AhR), and pentoxyresorufin-O-depenthylase (PROD) activity in the liver were determined. Marked histopathologic changes were observed in the thyroid glands, especially in the crows from the urban downtown area. Levels of dioxins and their toxic equivalents (TEQs) and AhR mRNA expression in the livers of the crows from the urban area were higher than those from the suburban area. There was a high correlation between the levels of TEQs and PROD activity. The results of the present study demonstrated that jungle crows possess AhR-mediated toxicologic pathways similar to those of mammals and suggest the possibility that the thyroidal changes observed in the adult crows from the urban areas are one of the toxic manifestations resulting from exposure to dioxins and other environmental chemicals.
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The electric quadrupole transition from the first 2(+) state to the ground 0(+) state in 16C is studied through measurement of the lifetime by a recoil shadow method applied to inelastically scattered radioactive 16C nuclei. The measured mean lifetime is 77+/-14(stat)+/-19(syst) ps. The central value of mean lifetime corresponds to a B(E2;2+(1)-->0(+)) value of 0.63e(2) fm(4), or 0.26 Weisskopf units. The transition strength is found to be anomalously small compared to the empirically predicted value.
Clinical studies have shown that pranlukast, a selective cysteinyl leukotriene antagonist, is effective for bronchial asthma. In the present paper, we retrospectively analyzed long-term asthma control by pranlukast treatment in patients treated with inhaled corticosteroids. We analyzed medical records and asthma diaries of 21 patients (9 males, 12 females) (52.1 +/- 3.5 years of age) with bronchial asthma who experienced increase of more than 10 L/min in peak expiratory flow in the first 4 weeks of treatment with pranlukast (450 mg/day) and were subsequently treated with pranlukast for more than 1 year. They all received inhaled corticosteroids (400-1600 microg/day of beclomethasone dipropionate or equivalent). We examined clinical control in terms of time course of self-monitored peak expiratory flow. During the analyzed period, the dose of inhaled corticosteroids was tapered in 4 patients, constant in 15 patients and increased in 2 patients. In 19 patients treated with unchanged or tapered dose of inhaled corticosteroids, improvement in the increase of mean PEF at 4-week treatment was maintained for 1 year. No difference in the add-on effect of pranlukast was observed in patients treated with less than 800 microg and more than or equal to 800 microg of inhaled corticosteroids. Four patients underwent reduction of inhaled corticosteroids in the analyzed period and PEF was well-maintained and even increased by pranlukast treatment. In 11 patients in whom data for 3 years were available, the improvement in PEF persisted for 3 years. Although the present investigation is a retrospective analysis, these data may suggest that pranlukast has no tachyphylaxis and its effect continues for more than 1 year.
Comparing the hydrogen content in aluminum hydroxides, one of the main components of Al-corrosion, with that in polyethylene sheets, corroded degree of practical Al-corrosions were estimated quantitatively by neutron radiography.
We compared morphologic changes in thyroid glands of great cormorants (Phalacrocorax carbo) from the Tokyo Bay and Lake Biwa areas in Japan with presence of residues of polychlorinated dibenzo-dioxins (PCDDs), polychlorinated dibenzo-furans (PCDFs), and coplanar polychlorinated biphenyls (Co-PCBs). Prominent morphologic changes in thyroid glands included increased density of small follicles and increased number of epithelial cells surrounding follicular lumens. The extent of morphologic changes in the thyroid gland was higher in cormorants captured from Tokyo Bay than in those captured from Lake Biwa. Increased thyroid change in cormorants from the Tokyo Bay area was associated with significantly higher levels of PCDFs and Co-PCBs. Thus, we suggest that morphologic changes in thyroid glands from the cormorants are associated with increased levels of dioxin contamination in Japan.
There are many reports on acute cerebral infarcts diagnosed by diffusion-weighted MRI (DWI), but few describe brain-stem infarcts diagnosed by this method. Using the apparent diffusion coefficient (ADC), we studied 18 consecutive patients with brain-stem infarcts who underwent DWI during the acute phase. We calculated and compared the ADC ratio (lesion ADC/contralateral ADC) in 10 patients with brain-stem and 23 with supratentorial cortical infarcts examined within 24 h of the onset of stroke. Ischaemic brain-stem lesions were detected in all 15 patients who underwent DWI more than 3 h after the onset, but not in two who had DWI within 3 h of the onset; their ADC ratio was more than 0.95. ADC ratios in patients with brain-stem infarcts decreased as the interval between onset and DWI increased; the decrease was slower than in patients with supratentorial cortical infarcts.