Tensile fatigue of a laminated carbon-carbon composite at room temperature

The tensile fatigue behavior of a cross-ply carbon-carbon (C/C) laminate was examined at room temperature. Tension-tension cyclic fatigue tests were conducted under load control at a sinusoidal frequency of 10 Hz to obtain stress-fracture cycles (S-N) relationship. The fatigue limit of the C/C was found to be 213 MPa (93% of the tensile strength), and no fracture was observed at over 10⁴ cycles. The residual tensile strength of specimens that survived fatigue loading was enhanced with increase in fatigue cycles and applied stress. Observations of the fatigue-loaded specimens revealed that the formation of micro-cracks at the fiber-matrix interfaces was facilitated during fatigue loading. These interfacial cracks were concluded to protect the fibers from being damaged by matrix cracks and this behavior was considered to be the governing mechanism of strength enhancement by fatigue loading.     

Electron-microscopic imaging of single-walled carbon nanotubes grown on silicon and silicon oxide substrates

Direct imaging of single-walled carbon nanotubes (SWNTs) suspended on pillar-patterned Si or SiO2 substrates is investigated using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The suspended nanotubes are successfully observed by direct TEM imaging and it is seen that they have either individual or bundles of SWNTs. Low energy (< or =2 keV) SEM produces high contrast images of suspended SWNTs. On the contrary, when SWNTs contact a SiO2 substrate, they are imaged using electron-beam induced current. The image brightness depends on the length of SWNTs.     

Potential of predominant activated sludge bacteria as recipients in conjugative plasmid transfer

We investigated the possibility of conjugative plasmid transfer to the predominant bacteria in activated sludge and the factors influencing the transfer frequency in the activated sludge process. We performed conjugative transfers of a self-transmissible, broad-host-range plasmid RP4 from Escherichia coli C600 to activated sludge bacteria by broth mating. Most of the activated sludge bacteria tested could acquire plasmid RP4, although the transfer frequencies varied from 8.8 x 10(-7) to 1.3 x 10(-2) transconjugants per recipient. The transfer frequencies in several strains were similar to, or higher than, that in intraspecific transfer to E. coli HB101. Matings under various environmental conditions showed that factors relevant to physiological activity, such as temperature and nutrient conditions, seemed to affect the transfer frequency. In addition, conjugative transfer was detected even in filtered raw and treated wastewaters. Thus, the predominant activated sludge bacteria seem to have sufficient potential as recipients in conjugative plasmid transfer under the conditions likely to occur in the activated sludge process. Transfer frequency was reduced by agitation in the presence of suspended solid. This may suggest that conjugative plasmid transfer is physically inhibited in aeration tanks.     

Arrest of motor neuron disease in wobbler mice cotreated with CNTF and BDNF

Ciliary neurotrophic factor (CNTF) and brain-derived neurotrophic factor (BDNF) each promote the survival and differentiation of developing motor neurons, but do so through distinct cellular signaling pathways. Administration of either factor alone has been shown to slow, but not to arrest, progression of motor neuron dysfunction in wobbler mice, an animal model of motor neuron disease. Because CNTF and BDNF are known to synergize in vitro and in ovo, the efficacy of CNTF and BDNF cotreatment was tested in the same animal mode. Subcutaneous injection of the two factors on alternate days was found to arrest disease progression in wobbler mice for 1 month, as measured by several behavioral, physiological, and histological criteria.     

Pseudomonas spp. convert metmyoglobin into deoxymyoglobin

Meat ‘reddening’ by bacteria was observed in chilled beef. To identify the reddening bacteria, isolates were inoculated onto beef and the changes in CIE L^*a^*b^* values monitored. As a result, two Pseudomonas spp., including Pseudomonas fragi which is commonly observed in raw meat, were selected and identified as reddening bacteria. The reddening was coincidentally occurred with the appearance of slime, and the increase in thiobarbituric acid-reactive substances (TBARS) was simultaneously suppressed. In myoglobin-containing nutrient broth, it is shown spectroscopically that P. fragi converted metmyoglobin into deoxymyoglobin. It was concluded that the meat reddening was due to the formation of deoxymyoglobin, induced by the very-low-oxygen tension brought about by Pseudomonad’s oxygen consumption: This oxygen depletion simultaneously suppressed TBARS increase.     

Detection and identification of Wolbachia endosymbionts from laboratory stocks of stored-product insect pests and their parasitoids

Endosymbiotic bacteria belonging to the genus Wolbachia are maternally inherited and can cause various effects on the reproductive system of their invertebrate hosts. Owing to their critical effects on insect reproduction, Wolbachia are potential tools for future insect pest control strategies. Here, we explored Wolbachia infections among stock collections at the National Food Research Institute of Japan, where stored-product insect pests and their parasitoids are maintained. Diagnostic polymerase chain reactions (PCRs) and sequencing of a fragment of the Wolbachia surface protein (wsp) gene revealed that, among 59 strains (38 species) belonging to the Coleoptera, Psocoptera, Lepidoptera and Hymenoptera, 18 strains (13 species) were infected with Wolbachia. Among them, 14 strains of Wolbachia were identified based on wsp gene sequences. Database searches showed that at least 6 Wolbachia strains were shared by multiple host species. Co-infections with two distinct Wolbachia strains were found in the drugstore beetle Stegobium paniceum and Angoumois grain moth Sitotroga cerealella. Detection and characterization of Wolbachia strains from these pests and their parasitoids provide us with basic information for future pest control strategies using these endosymbiotic bacteria.     

Dynamic characteristics and dual control of a ball screw drive with integrated piezoelectric actuator

This paper describes the precision continuous path tracking control by using a dual-actuated single stage. First, fine-drive mechanism and the dynamic model of the entire drive system are described. In the simulation model, the dynamic characteristic of the dual-actuated stage is investigated to see whether it can provide precise motion by using dual control. Second, the fine motion controller is designed. Adjusting the control parameters, a positioning resolution of 20 nm and a bandwidth of 260 Hz were obtained. Third, the frequency responses of coarse and fine drives are experimentally investigated. After that, the dual controller is designed based on the investigated dynamics. Finally, whether coarse motion and fine motion could work complimentarily by the dual servo is examined in the experiments. By using the simultaneous dual controller, tracking errors were reduced sufficiently compared to the single coarse control.