Dynamics of low-intermediate-high-confinement transitions in toroidal plasmas

The dynamic features of the low-intermediate-high-(L-I-H) confinement transitions on HL-2A tokamak are presented. Here we report the discovery of two types of limit cycles (dubbed type-Y and type-J), which show opposite temporal ordering between the radial electric field and turbulence intensity. In type-Y, which appears first after an L-I transition, the turbulence grows first, followed by the localized electric field. In contrast, the electric field leads type-J. The turbulence-induced zonal flow and pressure-gradient-induced drift play essential roles in the two types of limit cycles, respectively. The condition of transition between types-Y and -J is studied in terms of the normalized radial electric field. An I-H transition is demonstrated to occur only from type-J.

Collective excitation of an electric dipole on a molecular dimer in an organic dimer-Mott insulator

The terahertz response in 10-100 cm(-1) was investigated in an organic dimer-Mott (DM) insulator κ-(ET)(2)Cu(2)(CN)(3) that exhibits a relaxorlike dielectric anomaly. An ~30 cm(-1) band in the optical conductivity was attributable to collective excitation of the fluctuating intradimer electric dipoles that are formed by an electron correlation. We succeeded in observing photoinduced enhancement of this ~30 cm(-1) band, reflecting the growth of the electric dipole cluster in the DM phase. Such optical responses in κ-(ET)(2)Cu(2)(CN)(3) reflect an instability near the boundary between the DM-ferroelectric charge ordered phases.

Observation of long-distance radial correlation in toroidal plasma turbulence

This Letter presents the discovery of macroscale electron temperature fluctuations with a long radial correlation length comparable to the plasma minor radius in a toroidal plasma. Their spatiotemporal structure is characterized by a low frequency of ∼1-3  kHz, ballistic radial propagation, a poloidal or toroidal mode number of m/n=1/1 (or 2/1), and an amplitude of ∼2% at maximum. Nonlinear coupling between the long-range fluctuations and the microscopic fluctuations is identified. A change of the amplitude of the long-range fluctuation is transmitted across the plasma radius at the velocity which is of the order of the drift velocity.

Uneven distribution of the luxS gene within the genus Campylobacter

Polymerase chain reaction (PCR) amplification was performed on 20 isolates of five Campylobacter species using a degenerate primer pair designed in silico to generate a product of the luxS gene or its homologue from Campylobacter organisms. Although the primer pair successfully amplified products of approximately 500 base pairs (bp) with the eight isolates of C. jejuni and C. coli and some of C. upsaliensis and C. fetus, it failed to amplify fragments with all four isolates of C. lari (two urease-negative C. lari; two urease-positive thermophilic campylobacters). When Southern blot hybridisation analysis was carried using the mixed luxS gene fragments prepared from the C. jejuni, C. coli, C. upsaliensis and C. fetus strains as a probe, all C. jejuni, C. coli, C. upsaliensis and C. fetus isolates gave positive signals, but no positive signal was detected with any C. lari isolate. These results clearly indicate that C. jejuni, C. coli, C. upsaliensis and C. fetus carry the luxS gene or its homologue. However, no luxS gene or its homologue was identified to occur in the C. lari genome. Although autoinducer-2 assays were positive in C. jejuni, C. coli, C. upsaliensis and C. fetus isolates, it was negative with all the C. lari isolates examined. In addition, a biofilm formation assay demonstrated that biofilm formation in the C. lari species does not appear to correlate with the occurrence of the luxS gene because biofilm formation occurred among some isolates of C. lari.

Design of species-specific oligonucleotide probes for the detection of Bacteroides and Parabacteroides by fluorescence in situ hybridization and their application to the analysis of mouse caecal Bacteroides-Parabacteroides microbiota

AIMS

To develop species-specific monitoring techniques for rapid detection of Bacteroides and Parabacteroides inhabiting the mouse intestine by fluorescence in situ hybridization.

METHODS AND RESULTS

The specificity of oligonucleotide probes was evaluated by fluorescence whole-cell hybridization. Oligonucleotide probes specific for each species hybridized only with the target bacteria. Using these probes, caecal Bacteroides-Parabacteroides microbiota of conventional mice and specific pathogen-free (SPF) mice from three different breeders were analysed. It was shown that Bacteroides acidifaciens Group-1, Group-2 and Group-3 were dominant in conventional mice and SPF mice from two out of three breeders. Bacteroides vulgatus and Parabacteroides distasonis were detected in one of these two SPF breeding colonies in addition to Bact. acidifaciens. SPF mice of the remaining breeder harboured characteristic Bacteroides-Parabacteroides microbiota, consisting of Bacteroides sp. ASF519 and Bacteroides caccae.

CONCLUSIONS

Bacteroides acidifaciens is the dominant and most typical species in the mouse Bacteroides-Parabacteroides microbiota. The Group-3 was identified as a novel group and revealed to occupy a major niche together with Bact. acidifaciens Group-1 and Group-2.

SIGNIFICANCE AND IMPACT OF THE STUDY

The species-specific probe set developed in this study was the efficient tool for rapid detection of target bacterial groups inhabiting the mouse intestine. The results of this study provide important new information on the mouse Bacteroides-Parabacteroides community.

Vapor Phase Epitaxy of GaN Using Gallium Tri-Chloride and Ammonia

GaN films with good crystalline quality are grown on sapphire by atmospheric pressure vapor phase epitaxy using gallium tri-chloride (GaCl3) and ammonia (NH3). Epitaxial growth is carried out over temperature and V/III-ratio ranges of 800–1000°C and 100–1000, respectively. Typical growth rate obtained is in the range of 5–20 μm/hr. The films grown below 925°C typically show three dimensional (island) growth, while above that temperature, continuous films are obtained. Films grown at 975°C with a V/III ratio > 300 exhibit a smooth surface. XRD analysis shows that the films are single crystal with hexagonal polytype. Strong band-edge photoluminescence is observed with a FWHM of 60 meV at room temperature and 25 meV at 77K. The results indicate that this simple growth technique is effective for growing high quality bulk GaN, which can be used as a substrate for subsequent epitaxy. In order to further improve the surface morphology, a preliminary experiment on GaN growth on a thin GaN buffer layer prepared by gas source MBE is also presented.

Characterization of microbial consortia that reductively dechlorinate 4-chlorophenol and transform phenol to benzoate enriched from estuarine sediment of Lake Shinji

Monochlorophenols were degraded to benzoate via phenol by the initial dechlorination and the subsequent conversion of phenol to benzoate in anaerobic sediment samples of estuarine Lake Shinji under methanogenic conditions. To characterize bacteria that dechlorinate 4-chlorophenol and transform phenol to benzoate, we analyzed the microbial community structure of the enrichment culture with each 4-chlorophenol and phenol by the limiting dilution method with polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) of 16S rRNA gene. After serial dilution of the culture, the 4-chlorophenol-dechlorinating culture consisted of two dominant bacteria, one of which was most homologous with Dehalobacter sp. In the enriched culture with phenol, minor band homologous with Cryptanaerobacter phenolicass corresponded to the transformation activity.

Observation of quasi-two-dimensional nonlinear interactions in a drift-wave streamer

A streamer, which is a bunching of drift-wave fluctuations, and its mediator, which generates the streamer by coupling with other fluctuations, have been observed in a cylindrical magnetized plasma. Their radial structures were investigated in detail by using the biphase analysis. Their quasi-two-dimensional structures were revealed to be equivalent with a pair of fast and slow modes predicted by a nonlinear Schrödinger equation based on the Hasegawa-Mima model.

Ultralow-repetition-rate, high-energy, polarization-maintaining, Er-doped, ultrashort-pulse fiber laser using single-wall-carbon-nanotube saturable absorber

An ultralow-repetition-rate, all-polarization-maintaining (PM), Er-doped, ultrashort-pulse fiber laser was demonstrated using a single-wall-carbon-nanotube polyimide film. Using a ring cavity configuration, output pulses with pulse energy of 0.7-2.6 nJ were obtained at an ultralow repetition rate of 943-154 kHz for a fiber length of 0.1-1.3 km. A novel θ (theta) cavity configuration was proposed, which enabled us to reduce the required fiber length by half. A repetition rate of 132 kHz was achieved using this configuration with 909 m of PM fiber.