Fracture mechanism of liquid‐crystalline epoxy resin systems with different phase structures

A liquid‐crystalline epoxy resin was cured at two different temperatures. The phases of the cured systems clearly showed isotropic and nematic polydomain structures, which depended on the curing temperature. The fracture toughness of the systems was measured, and the fracture mechanism was investigated with polarized IR measurements. The nematic polydomain structure system showed considerably higher fracture toughness than the isotropic structure. Moreover, both systems exhibited a reorientation of the network chains near the fracture surface during the fracture process, and the region of the network reorientation in the nematic polydomain structure system was larger than that in the isotropic structure system. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4044–4052, 2004     

Influence of the network chain orientation on the fracture toughness of a mesogenic epoxy resin modified with CTBN

A biphenol‐type epoxy resin, which had a mesogenic group in the backbone moiety, was modified with carboxy‐terminated butadiene acrylonitrile copolymer (CTBN) as a reactive elastomer, and its fracture toughness was measured. With the addition of CTBN, the fracture toughness of the biphenol‐type epoxy resin significantly increased and became significantly higher than that of a bisphenol A‐type epoxy resin modified with CTBN. The network chain orientation in the cured biphenol‐type epoxy resin system was clearly observed during the fracture process with polarized microscopy Fourier transform infrared measurements, although such a phenomenon was not observed in the bisphenol A‐type epoxy resin system. The high toughness of the cured biphenol‐type system was clearly due to the consumption of the mechanical energy by a large deformation of the matrix resin due to the orientation of the network chains during the fracture process. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1198–1209, 2003     

Thermal properties and fracture toughness of a liquid‐crystalline epoxy resin cured with an aromatic diamine crosslinker having a mesogenic group

A mesogenic‐type curing agent was synthesized to introduce a mesogenic group not only into epoxy resin backbones but also into the crosslink units. In the mesogenic curing agent system, the domain size became larger, and the network arrangement in each domain existed to a greater extent than that in a system cured with the ordinary diamine curing system according to the evidence from polarized optical micrographs and polarized Fourier transform infrared mapping measurements. Moreover, the fracture toughness of the system was considerably improved. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2486–2494, 2006     

Oxidation activity of Au nanoparticles on aerogel supports

We have prepared titania aerogel and titania-coated silica aerogel incorporating thiol-capped Au nanoparticles. Both composite materials showed high CO oxidation activity after they were calcined at 673 K. Compositional and morphological changes driven by calcination were evaluated with thermogravimetry and X-ray diffractometry. From the results, it was suggested that the nanoparticles transformed from a faulted to a near-regular FCC structure presumably in concert with the formation of firm contacts between the nanoparticles and the gel substrates. While the diameters of the Au particles in the titania aerogel considerably increased upon calcination, those in the titania-coated silica aerogel were almost unchanged. As a consequence, the latter composite aerogel showed higher activity for oxidation of CO.     

Controlling the Dual-Emission Character of Aryl-Modified o-Carboranes by Intramolecular CH⋅⋅⋅O Interaction Sites

It is still challenging to realize a dual-emission system, in which two luminescent bands simultaneously appear by photoexcitation, in solid with organic dyes due to the difficulty in regulation of electronic properties in the excited state and concentration quenching. o-Carborane is known to be a versatile platform for constructing solid-state emitters since the sphere boron cluster is favorable for suppressing intermolecular interactions and subsequently concentration quenching. Here, we show solid-state dual-emissive o-carborane derivatives. We prepared 4 types of o-carborane derivatives and found dual-emission behaviors both in solution and solid states. By regulating the rotation at the o-carborane unit with the intramolecular C_cageH⋅⋅⋅O interaction, the dual-emission intensity ratios were changed. Finally, it was demonstrated that the overall photoluminescence spectra can be estimated using the binding energy of intramolecular interactions.     

Technical study for SPECT of the head using slant hole collimator

The performance of a 160 keV slant hole collimator (160 keV SH) was compared with that of a 140 keV high resolution collimator (140 keV HR) for SPECT imaging of the head using 99mTc. The minimum radius of revolution was reduced from about 23 cm to 13 cm using 160 keV SH. Relative sensitivity of the 160 keV SH was 108% of that of the 140 keV HR. Compared with SPECT using 140 keV HR, 160 keV SH SPECT yielded approximately a 15% increase in resolution. The 160 keV SH SPECT images of phantom were superior in resolution and contrast to that of 140 keV HR SPECT. We concluded that high quality SPECT images of the head can be obtained from rotating gamma cameras equipped with slant hole collimators.     

Fluorometric sensing of the salt-induced B-Z DNA transition by combination of two pyrene-labeled nucleobases

We have developed a new fluorescent DNA sensor containing two pyrene-labeled nucleobases, (Pet)G and (Py)C, and the fluorescence color was altered by the salt-induced B-Z DNA transition.     

A study on exponential-size neighborhoods for the bin packing problem with conflicts

We propose an iterated local search based on several classes of local and large neighborhoods for the bin packing problem with conflicts. This problem, which combines the characteristics of both bin packing and vertex coloring, arises in various application contexts such as logistics and transportation, timetabling, and resource allocation for cloud computing. We introduce \({\mathcal O}(1)\) evaluation procedures for classical local-search moves, polynomial variants of ejection chains and assignment neighborhoods, an adaptive set covering-based neighborhood, and finally a controlled use of 0-cost moves to further diversify the search. The overall method produces solutions of good quality on the classical benchmark instances and scales very well with an increase of problem size. Extensive computational experiments are conducted to measure the respective contribution of each proposed neighborhood. In particular, the 0-cost moves and the large neighborhood based on set covering contribute very significantly to the search. Several research perspectives are open in relation to possible hybridizations with other state-of-the-art mathematical programming heuristics for this problem.     

Actinoperylone, a novel perylenequinone-type shunt product, from a deletion mutant of the actVA-ORF5 and ORF6 genes for actinorhodin biosynthesis in Streptomyces coelicolor A3(2)

A novel shunt product, actinoperylone, has been isolated from a deletion mutant of the actVA-ORF5 and ORF6 genes involved in the biosynthesis of a benzoisochromanequinone (BIQ) antibiotic actinorhodin (ACT) in Streptomyces coelicolor A3(2). Spectroscopic analysis revealed its perylenequinone-type skeleton with the four chiral centers, obviously derived from the dimerization of an ACT intermediate. The structure of actinoperylone indicates the essential role of ActVA-ORF5 in the oxygen introduction at C-6, which is common to the formation of BIQ chromophore. The present results also agree with the distribution of the actVA-ORF5 homologues in all known BIQ biosynthetic clusters in streptomycetes.