Female-produced oviposition deterrents of the cigarette beetle,Lasioderma serricorne (F.) (Coleoptera: Anobiidae)

Oviposition deterrents of the cigarette beetle,Lasioderma serricorne, were isolated from its adult body extract and found to be identical to (2S,3R,1'S)-2,3-dihydro-3,5-dimethyl-2-ethyl-6-(l-methyl-2-oxobutyl)-4H-pyran-4-one (-serricorone) and its lR-epimer (-serricorone) by spectroscopic evidence. Serricorone was previously found as one of the minor sex pheromone components of the same insect, and hence indicating bi-functional nature. The presence of two isomers in the body was proved by careful treatment. Each of them exhibited the same level of oviposition deterring activity, which was less potent than the crude body extract at an increased concentration.     

Enhancement of nucleoside phosphorylation activity in an acid phosphatase

Escherichia blattae non-specific acid phosphatase (EB-NSAP)possesses a pyrophosphate-nucleoside phosphotransferase activity,which is C-5'-position selective. Current mutational and structuraldata were used to generate a mutant EB-NSAP for a potentialindustrial application as an effective and economical proteincatalyst in synthesizing nucleotides from nucleosides. First,Gly74 and Ile153 were replaced by Asp and Thr, respectively,since the corresponding replacements in the homologous enzymefrom Morganella morganii reduced the K_m value for inosine andthus increased the productivity of 5'-IMP. We determined thecrystal structure of G74D/I153T, which has a reduced K_m valuefor inosine, as expected. The tertiary structure of G74D/I153Twas virtually identical to that of the wild-type. In addition,neither of the introduced side chains of Asp74 and Thr153 isdirectly involved in the interaction with inosine in a hypotheticalbinding mode of inosine to EB-NSAP, although both residues aresituated near a potential inosine-binding site. These findingssuggested that a slight structural change caused by an aminoacid replacement around the potential inosine-binding site couldsignificantly reduce the K_m value. Prompted by this hypothesis,we designed several mutations and introduced them to G74D/I153T,to decrease the K_m value further. This strategy produced a S72F/G74D/I153Tmutant with a 5.4-fold lower K_m value and a 2.7-fold higherV_max value as compared to the wild-type EB-NSAP.     

A multi-step strategy for cutting and purification of single-walled carbon nanotubes

A multi-step procedure has been developed to cut and purify single-walled carbon nanotubes (SWCNTs) from the pristine soot synthesized by catalytic chemical vapor decomposition, which contains significant amount of multiwalled carbon nanotube (MWCNT) impurities. The procedure involves refluxing in dilute HNO₃ solution followed by (NH₄)₂S₂O₈/H₂SO₄ ultrasonication and a novel ammonia heat treatment step. The metal impurities are removed in the HNO₃ refluxing step. In the (NH₄)₂S₂O₈/H₂SO₄ treatment step, the SWCNTs are cut uniformly into micrometer long, while the MWCNTs are selectively cut into very short curled pieces. These short MWCNT pieces and the amorphous carbon impurities are partly removed in the (NH₄)₂S₂O₈/H₂SO₄ treatment step, and most of them are finally removed by the final ammonia heat treatment. The ammonia heat treatment step also recovers the structures of SWCNTs by healing defects on the sidewall. The final SWCNT products have purity higher than 95%, a length distribution between 1 and 2 μm, and very few defects.     

Threshold Stress for Crack-Healing of Si3N4/SiC and Resultant Cyclic Fatigue Strength at the Healing Temperature

Si₃N₄/SiC composite ceramics were hot-pressed in order to investigate the crack-healing behavior under stress. Semi-elliptical surface cracks of 100 μm in surface length were made on each specimen. The pre-cracked specimens were crack-healed under cyclic or constant bending stress, and the resultant bending strength and cyclic fatigue strength were studied. The threshold stress for crack-healing was investigated at healing temperatures of 1000° and 1200°C. The cyclic fatigue strengths of crack-healed specimens were also investigated at healing temperatures of 900° and 1000°C. The main conclusions are as follows: (1) The threshold cyclic and constant stresses for crack-healing, below which pre-cracked specimens recovered their bending strength, were 300 MPa, which was 75% of the bending strength of the pre-cracked specimens and (2) the crack-healed specimens exhibited quite high cyclic fatigue strength at crack-healing temperatures of 900° and 1000°C.     

The Hydroamination of methyl acrylates with amines over zeolites

H-form zeolites, H-FAU and H-BEA have been studied as heterogeneous catalysts for the hydroamination. They catalyzed the reaction of methyl acrylate with aniline to give N-[2-(methoxycarbonyl)ethyl]aniline (1) as a main product. H-BEA and H-FAU zeolites efficiently catalyzed the hydroamination to afford anti-Markovnikov adduct as a main product. The conversion of aniline around 55–85% was achieved within 18 h over H-BEA and H-FAU zeolites with SiO₂/Al₂O₃ molar ratio of 25–30; however, the formation of N,N-bis[2-(methoxycarbonyl)ethyl]aniline (2) as a product of double addition of methyl acrylate to aniline has also been observed as a by-product over H-BEA and H-FAU catalysts. The influences of the reaction parameters such as temperature and catalyst amount, and type of α,β-unsaturated esters and amines have been also investigated.     

Determination of β-carotene in plasma,blood cells and buccal mucosa by electrochemical detection

The β-carotene concentrations in plasma, blood cells and buccal mucosal cells were determined by high-performance liquid chromatography with electrochemical detection. This method was 1,000 times more sensitive than the conventional spectrophotometric method. Polymorphonuclear cells and red blood cells had lower β-carotene levels than the other cells. After oral administration of 580 mg/day of all-trans β-carotene to human male volunteers for a week, the β-carotene concentrations in all cell types increased at least several times above the original levels.     

Development and motion control of a biped walking robot based on passive walking theory

This research aims to develop the biped walking robot that can walk on the horizontal ground and improve walking efficiency by utilizing the theory of the passive walking robot, namely the pendulum principle. For that, two motors were installed on the hip of the robot to generate the control torques to perform a walking motion. The computer simulations with dynamic model were carried out to investigate the walking capability of the system. Experimental robot was developed considering the calculated results. The proportional control law was used in walking experiment. The robot can walk on the horizontal ground with the proposed method.     

A study of living plant specimens by low-temperature scanning electron microscopy

Young fresh Tradescantia reflexa stamen hair cells were used to clarify the optimal conditions for direct viewing and taking photographs with a scanning electron microscope (SEM) equipped with a cryo-system. The rate of protoplasmic streaming in the cells was measured under an optical microscope after examining and photographing them in the SEM over a period of a few minutes. Almost the same rate of streaming (5.5 μm/second, 20°C) was observed in nonirradiated control cells and irradiated cells photographed in the SEM using an accelerating voltage of 10 kV with the cryo-stage at a temperature of – 15°C. (The specimen holder and specimen were not at this temperature, but, rather, probably somewhat higher.) Fresh plant organs, tissues, and cells were also tested under the same conditions. The fine structure was well preserved in detail. The procedures were as follows: (1) prompt attachment of fresh plant materials on an aluminum specimen holder with double-faced adhesive Scotch tape or a small amount of plastic adhesive for woodcraft; (2) setting the holder on the cryo-stage cooled to –15°C in advance and rapid evacuation; and (3) quick SEM examination and photography (within several minutes). The advantages of this method are summarized as follows: (1) high possibility of viewing living materials; (2) minimal artifacts: freedom from chemical fixation and additional procedures utilized in ordinary SEM specimen preparation; and (3) simplicity, speediness, and economy in preparation for viewing. Since the specimens were not likely to be frozen during quick examination and photography, this method might well be called “low-temperature SEM” (LT-SEM) as distinguished from “cryo-SEM”.     

生物膜氨氧化及对硫酸盐还原的影响

利用好氧生物转盘进行了生物膜脱氨的试验,测定了生物膜内硫酸盐还原与硝酸盐还原及DO之间的关系。结果表明:在进水NH4 -N为40 mg/L、HRT为5.49 h时,氨氧化率>85%;采用分段进水,合理利用碳源,有利于自养菌繁殖,从而促进硝化作用;由于受水力冲刷等作用的影响,在生物膜内DO扩散深度可达350μm左右(大于在污泥基团的扩散深度),只有在低DO的层面上才出现NO3--N的反硝化;在含有NO3--N的系统内,生物膜内硫酸盐还原作用减弱,表明硫酸盐还原与反硝化是相互影响的,这一结果对富含硫酸盐的有机废水生物脱氮处理有一定的参考价值。     

Joint inhomogeneity in dissimilar friction stir welded martensitic and nanostructured ferritic steels

Dissimilar welding between oxide dispersion strengthened ferritic (ODS) steel and reduced activation martensitic steel would be required for constructing the advanced blanket of progressive fusion reactors. In this study, we achieved dissimilar joints by friction stir welding, and aimed to characterise and ameliorate joint inhomogeneity. Main results reveal that the joint inhomogeneity is generated from discrepant microstructural evolutions within the martensitic and ODS ferritic steels. The ODS steel achieves evolution by the dynamic recrystallisation, while the martensitic steel undergoes phase transformation that drastically hardens the stir zone. By a proper post-weld heat treatment, the joint inhomogeneity can be effectively ameliorated due to carbide reprecipitation and stress relief in the joint.