Authors:Maria Marques, Cintia Matsumura, and H. Santo Neto
mice, lack of dystrophin leads to increases in calcium influx and myonecrosis, followed by muscle regeneration. Synapse elimination is faster in
than in controls, suggesting that increases in calcium influx during development could be involved. In the present study, we evaluated whether dystrophic fibers display changes in permeability to Evans Blue Dye (EBD) during development of the neuromuscular junction. EBD is a sensitive label for the early detection of increased myofiber permeability and sarcolemmal damage. After intraperitoneal injection of EBD, sternomastoid (STN) and tibialis anterior (T. anterior) muscles were analyzed with fluorescence microscopy. At 01, 07 and 14 days of age, STN and TA
myofibers were not stained with EBD. At 21 days of age, positive labeling of TA and STN
myofibers was seen, suggesting permeability modification and myonecrosis. Adult muscles showed a decrease (T. anterior) or no changes (STN) in the amount of EBD-positive fibers. These results suggest that there is no sarcolemmal damage detected by EBD during development of dystrophic neuromuscular junctions and other factors may contribute to the earlier synapse elimination seen in dystrophic muscle.
Authors:K. Masumoto, H. Matsumura, K. Bessho, and A. Toyoda
Activation is one of the severe problems at the high-energy accelerator facilities. By using gamma-ray spectrometry and activation
detector technique, we could obtain important information on (1) nuclear reactions, (2) energy spectra of secondary particles,
(3) penetration behavior of secondary particles in shield wall, (4) historical record of beam loss occurred in the accelerator
rooms. It was concluded that the technique and knowledge of activation analysis are very useful to solve the radiation protection
problems at the accelerator facilities.
Authors:H. Matsumura, K. Masumoto, A. Toyoda, and N. Kinoshita
Highly selective and sensitive γ-ray detection was performed by coincidence and anticoincidence event analysis after list-mode
data acquisition using an HPGe spectrometer equipped with NaI(Tl) and plastic scintillation detectors. In order to obtain
the most suitable detection of specific nuclides, coincidence or anticoincidence spectra could be freely constructed by extracting
events with particular time and energy correlations. Although the detector arrangement of this system was the same as that
of a typical Compton suppression spectrometer, background counts were drastically reduced and γ-rays of particular nuclides
could be selectively detected by using γ-γ, γ-X, γ-X-X, and γ-β+ coincidences.
Authors:T. Aze, M. Fujimura, H. Matsumura, K. Masumoto, N. Nakao, H. Matsuzaki, H. Nagai, and M. Kawai
In order to estimate the total radioactivity induced in a concrete shield by thermal neutron-capture reactions at high-energy
accelerator facilities, the observed activity of 36Cl in the concrete is expected to serve as an indicator of the thermal neutron fluence. Since 36Cl can also be produced from K and Ca by spallation reactions, we measured these production rates in order to clarify the
contribution of each reaction. The Cl, K, and Ca targets were irradiated with neutrons having a maximum energy of 500 MeV.
As a result, the production rates of 36Cl from Cl were only two orders higher than those from K and Ca. It was found that the 36Cl production ratios from Cl, K, and Ca were 6.7%, 6.8%, and 86.5%, respectively, and Ca was the main source of 36Cl production.
Authors:H. Haba, H. Matsumura, Y. Miyamoto, K. Sakamoto, Y. Oura, S. Shibata, M. Furukawa, and I. Fujiwara
The recoil properties of 26 radionuclides produced in the photonuclear reactions on Cu at bremsstrahlung end-point energies
(E0) of 250 to 1000 MeV have been investigated using the thick-target thick-catcher method. Kinematic properties of the product
nuclei were calculated by the two-step vector velocity model. The calculated mean kinetic energies,T, of product nuclei increase with increase of the mass difference between products and target, reflecting the resonance natures
and absorption mechanisms. TheT atE0≥600 MeV were well reproduced by a calculation performed by PICA code byGabriel andAlsmiller atE0=400 MeV, except for (γ,xn) products by giant-resonance.
Authors:H. Matsumura, T. Miura, S. Ishihama, N. Matsuda, T. Aze, K. Masumoto, and T. Suzuki
Gold activation detectors were placed at nine positions on the inner wall of the KEK neutrino target station, and were exposed
to secondary particles during approximately one month of machine operation. After exposure, the production rates of 19 spallation
nuclides, which were produced in the Au activation detectors by nuclear reactions with different threshold energies, were
determined by γ-ray spectrometry. Thus, it was indicated that the Au activation detector is a novel tool for obtaining the
distribution of various secondary particles with high intensity and high energy.
Authors:Q. Wang, K. Masumoto, K. Bessho, H. Matsumura, T. Miura, and T. Shibata
An infrared furnace (ULVAC RHL-410P) was newly applied to the extraction of tritium from concrete samples. After studying the tritium recovery yield regarding temperature and time, the best extraction conditions were set to 800 °C (setting temperature) for 30 minutes under Ar-gas flow of 200 ml/min. Tritium was collected in two cold traps and transferred to a vial for liquid scintillation counting. It took about one hour for the extraction of tritium. Reproducibility and recovery yield of tritium were about 100% compared to the values obtained by the ordinary heating method using an electric furnace. Gamma-ray emitters and tritium of concrete samples collected from several accelerator facilities have been determined. The specific activity of tritium strongly correlated with that of 152Eu and 60Co, so it was found that tritium was produced by thermal neutron reaction by the 6Li(n,)3H reaction. The results indicate that the tritium specific activity in concrete can be estimated from the 60Co specific activity obtained easily by -ray measurement.
Authors:Q. Wang, K. Masumoto, K. Bessho, H. Matsumura, T. Miura, and T. Shibata
For evaluation of radioactivity induced in the concrete samples from accelerator facilities, the residual radioactivity in
concrete sample, collected from seven accelerator facilities, was determined by γ-ray spectrometry. The tritium was extracted
by the heating method using an IR furnace, and measured with a liquid scintillation counter. It was found that the major radioisotopes
activated mainly by neutrons in the concrete samples were 152Eu, 60Co, 134Cs and 3H. The concentrations of radioactivities induced by thermal neutron capture are the highest at a depth of 10 cm in the concrete
wall. The correlation between tritium, 60Co and 152Eu activity was investigated by measuring many concrete samples for seven accelerator facilities. The results indicate that
their activities are strongly correlated with each other. So it would also be concluded that the total activity in shielding
concrete could be estimated on the basis of the activities of 60Co and 152Eu.
Authors:K. Ninomiya, H. Sugiura, T. Nakatsuka, Y. Kasamatsu, H. Kikunaga, W. Sato, T. Yoshimura, H. Matsumura, K. Takamiya, M. Kubo, K. Sueki, A. Yokoyama, Y. Hamajima, T. Miura, K. Nishiyama, and A. Shinohara
The electronic X-ray energies of muonic atoms were precisely measured. The atomic number (Z) dependence of the energy difference between electronic X-rays of muonic atoms and Z-1 atoms (energy shift) was systematically investigated. The energy shifts in the low-Z region were compared with those of the high-Z region that had been obtained experimentally and theoretically in previous work. An obvious difference between these two
regions was found in the atomic-number dependence of the energy shift. We also compared the energy shifts of muonic atoms
with those of pionic atoms.