H-atom relay reactions in real space

Hydrogen bonds are the path through which protons and hydrogen atoms can be transferred between molecules. The relay mechanism, in which H-atom transfer occurs in a sequential fashion along hydrogen bonds, plays an essential role in many functional compounds. Here we use the scanning tunnelling microscope to construct and operate a test-bed for real-space observation of H-atom relay reactions at a single-molecule level. We demonstrate that the transfer of H-atoms along hydrogen-bonded chains assembled on a Cu(110) surface is controllable and reversible, and is triggered by excitation of molecular vibrations induced by inelastic tunnelling electrons. The experimental findings are rationalized by ab initio calculations for adsorption geometry, active vibrational modes and reaction pathway, to reach a detailed microscopic picture of the elementary processes.     

Stability and characterization of phospholipid Langmuir-Blodgett films

The regularity of the bilayer structure was compared between dipalmitoylphosphatidic acid (DPPA) Langmuir-Blodgett (LB) films and “oriented multilayers” of DPPA, using X-ray diffraction and electron spectroscopy for chemical analysis (ESCA). The angular variation of the (001) Bragg spot due to the irregularity of the lamellar repeat was remarkable in the system of oriented multilayers. In contrast, the spot of DPPA LB films exhibited only a slight angular variation, suggesting a regular structure of this film. The take-off angle dependence of the phosphorus:carbon ratio obtained by ESCA indicates that the regular layered structure in DPPA LB film is maintained after 49 layers are deposited.     

Effects of geometry and specimen size on out-of-plane tensile strength of aligned CFRP determined by direct tensile method

The out-of-plane tensile strength of CFRP laminate determined by the direct tensile method varies with specimen geometry and size. This effect was first experimentally observed using aligned CFRP. To explain the geometry and size effects from a mechanical point of view, an analytical model combining Weibull statistics, including the concept of effective volume, and a fracture criterion under multi-axial loading was constructed on the basis of stress distributions calculated using the finite element method. The predicted out-of-plane tensile strength of aligned CFRP was found to be consistent with experimental results. Thus, the present model is useful for reducing experimentally determined out-of-plane tensile strength under complex stress distributions to that under a uniaxial and uniform stress distribution.     

Effects of visual cue and spatial distance on exitability in electronic negotiation

We examined the effects of the visual anonymity of self and spatial distance on exitability in electronic negotiation in a role-play experiment. Exitability is the psychological factor that causes one to perceive the negotiation as unstable. We predicted that the lack of visual information and the spread of spatial distance would reduce anticipation of retaliation, make the continuation norm less salient, and prompt to exit from the current negotiation. Visual anonymity was manipulated by two conditions (visual anonymity or non-anonymity conditions). Spatial distance was manipulated by two conditions (remote or close conditions). Forty-three students were assigned in one of these four conditions, and negotiated. The results showed both the visual anonymity and remote distance inhibited the activation of continuation norm, prompted to exit from the current negotiation.     

Two nearly identical aromatic compound hydrolase genes in a strong polychlorinated biphenyl degrader, Rhodococcus sp. strain RHA1

The two 2-hydroxy-6-oxohepta-2,4-dienoate (HOHD) hydrolase genes, etbD1 and etbD2, were cloned from a strong polychlorinated biphenyl (PCB) degrader, Rhodococcus sp. strain RHA1, and their nucleotide sequences were determined. The etbD2 gene was located in the vicinity of bphA gene homologs and encoded an enzyme whose amino-terminal sequence was very similar to the amino-terminal sequence of the HOHD hydrolase which was purified from RHA1. Using the etbD2 gene fragment as a probe, we cloned the etbD1 gene encoding the purified HOHD hydrolase by colony hybridization. Both genes encode a product having 274 amino acid residues and containing the nucleophile motif conserved in alpha/beta hydrolase fold enzymes. The deduced amino acid sequences were quite similar to the amino acid sequences of the products of the single-ring aromatic hydrolase genes, such as dmpD, cumD, todF, and xylF, and not very similar to the amino acid sequences of the products of bphD genes from PCB degraders, including RHA1. The two HOHD hydrolase genes and the RHA1 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate (HPDA) hydrolase gene, bphD, were expressed in Escherichia coli, and their relative enzymatic activities were examined. The product of bphD was very specific to HPDA, and the products of etbD1 and etbD2 were specific to HOHD. All of the gene products exhibited poor activities against the meta-cleavage product of catechol. These results agreed with the results obtained for BphD and EtbD1 hydrolases purified from RHA1. The three hydrolase genes exhibited similar induction patterns both in an RNA slot blot hybridization analysis and in a reporter gene assay when a promoter probe vector was used. They were induced by biphenyl, ethylbenzene, benzene, toluene, and ortho-xylene. Strain RCD1, an RHA1 mutant strain lacking both the bphD gene and the etbD2 gene, grew well on ethylbenzene. This result suggested that the etbD1 gene product is involved in the meta-cleavage metabolic pathway of ethylbenzene.     

Effect of Shear Damage on the Fracture Behavior of Carbon–Carbon Composites

The notch insensitivity of carbon–carbon composites (C/Cs) has been believed to result primarily from shear damage near sources of stress concentration. To evaluate this hypothesis, notch sensitivity has been examined for C/Cs with crossply laminates (CP-C/Cs) and quasi-isotropic (QI-C/Cs) laminates. The main difference in both laminates involves their shear behavior: the QI-C/Cs have an almost-linear stress–strain curve and high strength, whereas the CP-C/Cs exhibit strong nonlinearity and low strength. Thus, the effect of shear damage can be extracted by comparison of both materials. Experimental results from the present study have shown that the fracture behaviors of both C/Cs are quite similar. Finite-element analyses also have revealed that the stress redistribution caused by shear nonlinear deformation is too small to explain its toughening behavior, even in the CP-C/C. From these results, it is concluded that the notch-insensitive behavior of the C/Cs cannot be explained by the already-proposed shear-damage mechanism. To this end, a discussion has been conducted on a new possible toughening mechanism that is capable of generating the R -curve and notch insensitivity.     

Analysis of gas leakage through C/C composites

Gas leakage through carbon-fiber-reinforced carbon matrix composites (C/Cs) was examined with respect to the application of C/Cs in heat exchangers in an engine system for a future space plane. Because C/Cs have many cracks and pores, gas readily leaks through them. To predict and prevent this gas flow through the C/Cs, leakage rates were measured as a function of pressure, and gas flow paths were identified by microscopic observations of C/Cs. Several analytical models were then used to clarify the principal mechanisms yielding gas-flow resistance. Laminar flow models in tubes and slits were found to give excellent leak-rate predictions compared with experimental results for unidirectionally and three-dimensionally reinforced C/Cs, respectively. A model based on adiabatic expansion and compression, which is used for gas leaks through labyrinth seals, resulted in reasonable agreement with the leak rates through a cross-ply laminated C/C.     

Effect of temperature and layer thickness on these strengths of carbon bonding for carbon/carbon composites

In order to apply carbon/carbon composites (C/Cs) to various hot structures, secondary bonding techniques effective at elevated temperatures are frequently required. In the present study, carbon bonding between lamination type C/Cs was formed by the carbonation of polymer adhesive, and the strength of the bonding was evaluated at temperatures up to 2273 K in a vacuum using the double-notched shear method. The results revealed that bonding strength increased with increasing temperature and became higher than the inter-laminar shear strength of the substrate C/C when the bonding layer was thin. The enhancement of carbon bonding strength with increasing temperature was shown to be caused mainly by the evaporation of absorbed gases, probably water, up to temperatures of 1800 K with a slight additional contribution of thermal residual stress. It was also shown that heat treatment at higher temperatures made the bonding stronger.