K. H. Tanaka

Formation of A = 12. sigma. /sup -/ hypernucleus from K/sup -/ absorption at rest; Observation of a. sigma. /sup -/ spin-orbit doublet of narrow widths

High-resolution spectroscopy of ..pi../sup +/ from K/sup -/ absorption at rest has been used for the first time to identify ..sigma../sup -/ hypernuclear states. The observed spectrum from a (CH)/sub n/ target has revealed a p/sub 3/2/-p/sub 1/2/ doublet of /sup 12/Be with narrow widths. The spin-orbit splitting of ..sigma../sup -/ is deduced to be 5 MeV, 0.8 times that for nucleons.

Purification and characterization of oxygen-inducible haem catalase from oxygen-tolerant Bifidobacterium asteroides.

Bifidobacterium asteroides, originally isolated from honeybee intestine, was found to grow under 20% O(2) conditions in liquid shaking culture using MRS broth. Catalase activity was detected only in cells that were exposed to O(2) and grown in medium containing a haem source, and these cells showed higher viability on exposure to H(2)O(2). Passage through multiple column chromatography steps enabled purification of the active protein, which was identified as a homologue of haem catalase on the basis of its N-terminal sequence. The enzyme is a homodimer composed of a subunit with a molecular mass of 55 kDa, and the absorption spectrum shows the typical profile of bacterial haem catalase. A gene encoding haem catalase, which has an amino acid sequence coinciding with the N-terminal amino acid sequence of the purified protein, was found in the draft genome sequence data of B. asteroides. Expression of the katA gene was induced in response to O(2) exposure. The haem catalase from B. asteroides shows about 70-80% identity with those from lactobacilli and other lactic acid bacteria, and no homologues were found in other bifidobacterial genomes.

Modification of the magnetic field structure of high-beta plasmas with a perturbation field in the Large Helical Device

The effect of resonant magnetic perturbation (RMP) on MHD characteristics is investigated in high-beta plasmas of the Large Helical Device. The ramp-up and static m/n = 1/1 RMP field are applied in medium- (~2%) and high- (~4%) beta plasmas in order to find beta dependences of mode penetration, MHD activities and confinement. The results show that the threshold of mode penetration linearly increases with the beta value and/or plasma collisionality. The threshold of mode penetration in the RMP ramp-up experiments is roughly consistent with the static RMP case. The beta value gradually decreases with the RMP field strength before mode penetration, which is caused by a reduction in the pressure inside the ι/2π = 1 resonance. The width of the magnetic island after the penetration becomes larger than the given RMP field, and it is further enhanced by the increment of the beta value.

Observation of flow reversal in plasmas with a neoclassical internal transport barrier in CHS

A reversal of toroidal flow is observed in plasmas where a large positive electric field and a sharp electron temperature gradient are sustained inside the internal transport barrier in a compact helical system. This observation shows that the spontaneous toroidal flow in the direction anti-parallel to the Er×Bθ drift becomes large enough to reverse the toroidal flow driven by a tangentially injected neutral beam. The difference in the direction and the magnitude of the spontaneous toroidal flow are also discussed.

A new type of λ hypernuclear spectroscopy using stopped K− with efficient background supression

Abstract A new tagging method is proposed to suppress the continuous background in Π − spectra in λ hypernuclear spectroscopy using stopped K − . A Monte Carlo simulation was made for 40 Ca(stopped K − , Π − ) λ 40 Ca. This method appears promising in identifying ground and low-lying orbitals of λ in medium and heavy nuclei.

Suppression of Trapped Energetic Ions Driven Resistive Interchange Modes with Electron Cyclotron Heating in a Helical Plasma

The resistive interchange mode destabilized by the resonant interaction with the trapped energetic ions is fully suppressed when the injected power of electron cyclotron heating exceeds a certain threshold. It is shown for the first time that the complete stabilization of the energetic-particle-driven mode without relaxing the energetic particle (EP) pressure gradient is possible by reducing the radial width of the eigenmodes δ_{w}, especially when δ_{w} narrows to a small enough value relative to the finite orbit width of EP.

A measurement of the π0 decay of Λ 12 C and Λ 11 B hypernucleihypernuclei

SummaryWe made a direct measurement of the π0 weak decay branching ratio of theΛ12C hypernucleus for the first time. The branching ratio is estimated to beΓπ0/Γ=0.166±0.055 from the measurement. The branching ratio agrees fairly with a theoretical calculation with a realistic pion distorted wave function, but is inconsistent with a calculation with a free π0 wave function. An upper limit of the π0 decay branching ratio of theΛ11B hypernucleus was also estimated to beΓπ0/Γ<0.291 (90% confidence level).RiassuntoÈ stata misurata direttamente la frazione di decadimento (debole) dell’ipernucleoΛ12C in π0 per la prima volta. Dalla misura risulta cheΓπ0/Γ=0.166±0.055. Il rapporto coincide con il calcolo teorico con una funzione d’onda distorta realistica pionica, ma non è in accordo con il calcolo con la funzione d’onda libera del pione. Anche il limite superiore stimato del rapporto di decadimento pionico dell’ipernucleoΛ11B èΓπ0/Γ<0.291 (livello di confidenza 90%).РеэюмеВпервые проводится прямое иэмерение отнощение ветвей π0 слабого распада гиперядерΛ12C. Иэ иэмерения оценивается отнощение ветвей, которое составляетΓπ0/Γ=0.166±0.055. Отнощение ветвей совпадает с теоретическим расчетом, испольэуюшим искаженную волновую функцию реального пиона, но не согласуется с вычислением для волновой функции свободного π0. Также оценивается верхний предел отнощения ветвей π0 распада гиперядраΛ11B, который составляетΓπ0/Γ<0.291 (с достоверностью 95%).

O 2 -inducible H 2 O 2 -forming NADPH oxidase is responsible for the hyper O 2 sensitivity of Bifidobacterium longum subsp. infantis

Bifidobacteria are beneficial anaerobes, and their O2 sensitivity levels differ among species as a function of unknown molecular mechanisms. Bifidobacterium longum subspecies infantis (B. infantis), a predominant colonizer of the gastrointestinal tract of infants, showed a hyper O2-sensitive growth profile with accompanying a production of H2O2. In this study, we characterized an NADPH oxidase as a key enzyme responsible for this microbe’s hyper O2 sensitivity. A dominant active elution peak of H2O2-forming NADPH oxidase activity was detected in the first step of column chromatography, and the purified NADPH oxidase (NPOX) was identified as a homolog of nitroreductase family proteins. The introduction of the gene encoding B. infantis NPOX (npoxA) into O2-tolerant Bifidobacterium minimum made the strain O2 sensitive and allowed it to produce H2O2. Knockout of the npoxA gene in B. infantis decreased the production of H2O2 and mitigated its B. infantis hyper O2 sensitivity. A transcript of B. infantis npoxA is induced by O2, suggesting that the aerobic production of toxic H2O2 is functionally conserved in B. infantis.

Search for 7Hat RIKEN

Experimental search for the low-lying {sup 7}H resonance was performed in the d({sup 8}He,{sup 3}He){sup 7}H reaction with a {sup 8}He beam at 42A MeV. No well-pronounced peak of {sup 7}H was observed, but the spectrum has some peculiarities at approx2 MeV and approx10.5 MeV above the t+4 n threshold. The d({sup 12}Be,{sup 3}He){sup 11}Li reaction simultaneously measured at 71A MeV showed the population of {sup 11}Li ground state with the c.m.s. cross section of approx =1 mb/sr.

Search for [sup 7]H at RIKEN

Experimental search for the low-lying {sup 7}H resonance was performed in the d({sup 8}He,{sup 3}He){sup 7}H reaction with a {sup 8}He beam at 42A MeV. No well-pronounced peak of {sup 7}H was observed, but the spectrum has some peculiarities at approx2 MeV and approx10.5 MeV above the t+4 n threshold. The d({sup 12}Be,{sup 3}He){sup 11}Li reaction simultaneously measured at 71A MeV showed the population of {sup 11}Li ground state with the c.m.s. cross section of approx =1 mb/sr.