KEKCB electron cyclotron resonance charge breeder at TRIAC.

The KEKCB is an electron cyclotron resonance (ECR) ion source for converting singly charged ions to multicharged ones at Tokai Radioactive Ion Accelerator Complex. By using the KEKCB, singly charged gaseous and nongaseous ions were converted to multicharged ones of A/q approximately 7 with efficiencies of 7% and 2%, respectively. The conversion efficiency was found to be independent of the lifetime of the radioactive nuclei having lifetimes of the order of one second. Three collimators located at the entrance and the exit of the KEKCB defined the beam axis and facilitated beam injection. Grinding and washing the surfaces of aluminum electrode and plasma chamber dramatically reduced impurities originating from the ECR plasma of the KEKCB.

Determination of the subthreshold state contribution in 13C(alpha,n)16O, the main neutron-source reaction for the s process.

The reaction rate of the stellar reaction 13C(alpha,n)16O, which is currently considered to be the main neutron source for the slow (s) process at low energies, has been rederived using the direct alpha-transfer reaction 13C(6Li,d)17O leading to the subthreshold state at 6.356 MeV in 17O. The contribution of the subthreshold state is found to be much smaller than the currently accepted predictions for the main neutron source of the s process, indicating less of a role of this reaction as the neutron source for the s-process scenario in low-mass stars at the asymptotic giant branch.

Isovector quadrupole resonance observed in the 60Ni(13C,13N)60Co reaction at E/A=100 MeV.

The charge-exchange reaction 60Ni(13C,13N)60Co at E/A=100 MeV has been studied to locate isovector (deltaT=1) non-spin-flip (deltaS=0) giant resonances. Besides the giant dipole resonance at E(x)=8.7 MeV, another resonance has been observed at E(x)=20 MeV with a width of 9 MeV. Distorted-wave Born approximation analysis on the angular distribution clearly indicated the L=2 multipolarity, attributing the E(x)=20 MeV state to the giant isovector quadrupole resonance.

Serotyping of Streptococcus pyogenes isolated from common and severe invasive infections in Japan, 1990-5: implication of the T3 serotype strain-expansion in TSLS. The Working Group for Group A Streptococci in Japan.

To clarify the relationship between the epidemics of severe invasive group A streptococcal infections (streptococcal Toxic Shock-Like Syndrome: TSLS) and common group A streptococcal infections in Japan, we examined the T serotypes of S. pyogenes strains (group A streptococci) isolated from clinical specimens of the streptococcal infections (17999 cases) in the period 1990-5, including the severe infections (TSLS) (29 cases) in the period 1992-5. Characteristic points of the analyses were: (1) dominant serotypes of the infections in these periods were T12, T4, T1, T28 and TB3264, which were consistently isolated; (2) isolates of T3 rapidly increased through 1990 to 1994 while T6 decreased in the period 1990-3; (3) when Japanese area was divided into three parts, T3 serotype tended to spread out from the north-eastern to the south-western area; (4) strains of T3 and T1 serotypes were dominant in the TSLS. Dominant-serotype strains of streptococcal infections did not always induce severe infections and dominance of T3 serotype in the TSLS seemed to be correlated with the increase of T3 in streptococcal infections. These results may indicate that certain clones of S. pyogenes are involved in the pathogenesis of the TSLS.

[Bacteriological studies on sporadic diarrhea diseases in Oita District, 1985-1996].

Approaching the problem of how close the sporadic diarrhea diseases correlate with epidemics of infectious diarrheas, including food poisonings, bacteriological studies were made on the characteristics of sporadic diarrheas in the past 10 years and analyzed. In collaboration with physicians, mostly pediatricians, in Oita district during 1985 to 1986 and 1989 to 1996, a total of 1707 specimens was obtained from diarrhea patients, suspected of bacterial cause. We have isolated 717 strains from 670 specimens (ca 40% of the total). The majority were; Campylobacter, Salmonella and EPEC with the rate of about 40, 24 and 23% respectively. On the other hand, isolation of Vibrio spp. and Staphylococcus were very few. The yearly trend of detection rates of such major agents were as follows: Campylobacter had the highest rate in the early period, 1989, but thereafter tended to decrease. In contrast, Salmonella continued to increase in rate through the study period until the present when it exceeds that of Campylobacter. This alternation is due primarily to the rapid increase of S. Enteritidis since its recent appearance. VTEC stays at a low rate with a slow increase showing no prevalence so far. From the above results the following may meet with attention. Vibrios and Staphylococci, known as popular agents for food poisonings, seem unlikely to correlate with sporadic diarrheas. Instead, the evidence that recent food poisoning is often represented by Salmonella, especially S. Enteritidis, suggests that epidemics of infectious diarrhea may be attributed to the background of common sporadic diarrheas.