RESUMEN
The Rare-RI Ring (R3) is a recently commissioned cyclotronlike storage ring mass spectrometer dedicated to mass measurements of exotic nuclei far from stability at Radioactive Isotope Beam Factory (RIBF) in RIKEN. The first application of mass measurement using the R3 mass spectrometer at RIBF is reported. Rare isotopes produced at RIBF-^{127}Sn, ^{126}In, ^{125}Cd, ^{124}Ag, ^{123}Pd-were injected in R3. Masses of ^{126}In, ^{125}Cd, and ^{123}Pd were measured whereby the mass uncertainty of ^{123}Pd was improved. This is the first reported measurement with a new storage ring mass spectrometry technique realized at a heavy-ion cyclotron and employing individual injection of the preidentified rare nuclei. The latter is essential for the future mass measurements of the rarest isotopes produced at RIBF. The impact of the new ^{123}Pd result on the solar r-process abundances in a neutron star merger event is investigated by performing reaction network calculations of 20 trajectories with varying electron fraction Y_{e}. It is found that the neutron capture cross section on ^{123}Pd increases by a factor of 2.2 and ß-delayed neutron emission probability, P_{1 n}, of ^{123}Rh increases by 14%. The neutron capture cross section on ^{122}Pd decreases by a factor of 2.6 leading to pileup of material at A=122, thus reproducing the trend of the solar r-process abundances. The trend of the two-neutron separation energies (S_{2n}) was investigated for the Pd isotopic chain. The new mass measurement with improved uncertainty excludes large changes of the S_{2n} value at N=77. Such large increase of the S_{2n} values before N=82 was proposed as an alternative to the quenching of the N=82 shell gap to reproduce r-process abundances in the mass region of A=112-124.
RESUMEN
Interaction cross sections for ^{42-51}Ca on a carbon target at 280 MeV/nucleon have been measured for the first time. The neutron number dependence of derived root-mean-square matter radii shows a significant increase beyond the neutron magic number N=28. Furthermore, this enhancement of matter radii is much larger than that of the previously measured charge radii, indicating a novel growth in neutron skin thickness. A simple examination based on the Fermi-type distribution, and mean field calculations point out that this anomalous enhancement of the nuclear size beyond N=28 results from an enlargement of the core by a sudden increase in the surface diffuseness of the neutron density distribution, which implies the swelling of the bare ^{48}Ca core in Ca isotopes beyond N=28.
RESUMEN
The nuclear shell structure, which originates in the nearly independent motion of nucleons in an average potential, provides an important guide for our understanding of nuclear structure and the underlying nuclear forces. Its most remarkable fingerprint is the existence of the so-called magic numbers of protons and neutrons associated with extra stability. Although the introduction of a phenomenological spin-orbit (SO) coupling force in 1949 helped in explaining the magic numbers, its origins are still open questions. Here, we present experimental evidence for the smallest SO-originated magic number (subshell closure) at the proton number six in 13-20C obtained from systematic analysis of point-proton distribution radii, electromagnetic transition rates and atomic masses of light nuclei. Performing ab initio calculations on 14,15C, we show that the observed proton distribution radii and subshell closure can be explained by the state-of-the-art nuclear theory with chiral nucleon-nucleon and three-nucleon forces, which are rooted in the quantum chromodynamics.
RESUMEN
Preclinical and clinical studies were performed to evaluate usefulness and safety of aztreonam (AZT) in the treatment of acute otitis media, acute exacerbation of chronic otitis media and chronic otitis media and the following results were obtained. MICs for P. aeruginosa, P. mirabilis and P. inconstans isolated from the patients with suppurative otitis media were 1.56 micrograms/ml, less than or equal to 0.025 micrograms/ml and less than or equal to 0.025 micrograms/ml respectively in their peaks. In the intravenous injection of 1 g, AZT concentration in the mastoid cell mucosa was 7.52 micrograms/g on average and serum concentration 51.6 micrograms/ml sufficiently suggesting clinical efficacy of AZT. In the clinical trial by administering AZT 1-2 g/day for the patients with suppurative otitis media, effective rates were 2/3 (66.7%) for acute otitis media, 16/22 (72.7%) for acute exacerbation of chronic otitis media, 21/34 (61.8%) for chronic otitis media and 6/7 (85.7%) for cholesteatoma of the middle ear. Elimination rate of single Gram-negative pathogens was 82.1% in the bacteriological studies of AZT. As for abnormal laboratory findings, 7 cases showed GOT, GPT elevations. However, they were in minor degree and transient. Side effect was not noted except 1 case of flushing with itching. It was considered from the above results that AZT is a highly useful antibiotic for suppurative otitis media.