Some Results for Range of Random Walk on Graph with Spectral Dimension Two

Journal of Theoretical Probability - We consider the range of the simple random walk on graphs with spectral dimension two. We give a form of strong law of large numbers under a certain uniform...     

Developments of nano-polycrystalline diamond anvil cells for neutron diffraction experiments

ABSTRACT

A new high pressure cell for neutron diffraction experiments using nano-polycrystalline anvils is presented. The cell design, off-line pressure generation tests and a gas-loading procedure for this cell are described. The performance is illustrated by powder neutron diffraction patterns of ice VII to ～82?GPa. We also demonstrate the feasibility of single crystal neutron diffraction experiments of Fe₃O₄ at ambient conditions using this cell and discuss the current limitation and future developments.     

Fabrication of Carbon Nanotube Thin Films for Flexible Transistors by Using a Cross-Linked Amine Polymer

Owing to their remarkable properties, single-walled carbon nanotube thin-film transistors (SWCNT-TFTs) are expected to be used in various flexible electronics applications. To fabricate SWCNT channel layers for TFTs, solution-based film formation on a self-assembled monolayer (SAM) covered with amino groups is commonly used. However, this method uses highly oxidized surfaces, which is not suitable for flexible polymeric substrates. In this work, a solution-based SWCNT film fabrication using methoxycarbonyl polyallylamine (Moc-PAA) is reported. The NH₂-terminated surface of the cross-linked Moc-PAA layer enables the formation of highly dense and uniform SWCNT networks on both rigid and flexible substrates. TFTs that use the fabricated SWCNT thin film exhibited excellent performance with small variations. The presented simple method to access SWCNT thin film accelerates the realization of flexible nanoelectronics.     

Photoinduced Pyramidal Inversion Behavior of Phosphanes Involved with Aggregation-Induced Emission Behavior

Aggregation-induced emission (AIE) is a fascinating phenomenon because of the applications of luminescent materials in the aggregated state, which exploit the large structural changes of the molecules in the excited state. Recently, it was reported that triphenylphosphane derivatives show AIE behavior in which they undergo potentially large structural changes in the excited state. Inspired by this report, photoinduced pyramidal inversion behavior of phosphanes was investigated. In photochemical experiments, the prepared P-stereogenic phosphanes exhibited photoracemization in dilute solution, and a negative correlation was observed between the photoracemization and the AIE phenomenon. Theoretical computations revealed that the inversion barrier in the excited state was much smaller than that in the ground state. This is the first report on the photoinduced pyramidal inversion behavior of phosphanes, which will provide new and unexplored applications.     

Total Synthesis of Terpioside B

The first total synthesis of terpioside B ( 1 ) has been accomplished. Key steps include the stereoselective installments of a set of challenging 1,2-cis-glycosidic linkages. Thus, α(1,4)-linked d -galactoside was effectively constructed from a 1,2-anhydrogalactose donor and an unprotected 1,6-anhydrogalactose acceptor by using a boron-mediated aglycon delivery (BMAD) method. In addition, α-l -fucofuranosides were stereoselectively and simultaneously constructed by remote group-assisted 1,2-cis-α-stereoselective glycosylations.     

High‐performance liquid chromatography separation of unsaturated organic compounds by a monolithic silica column embedded with silver nanoparticles

The optimization of a porous structure to ensure good separation performances is always a significant issue in high‐performance liquid chromatography column design. Recently we reported the homogeneous embedment of Ag nanoparticles in periodic mesoporous silica monolith and the application of such Ag nanoparticles embedded silica monolith for the high‐performance liquid chromatography separation of polyaromatic hydrocarbons. However, the separation performance remains to be improved and the retention mechanism as compared with the Ag ion high‐performance liquid chromatography technique still needs to be clarified. In this research, Ag nanoparticles were introduced into a macro/mesoporous silica monolith with optimized pore parameters for high‐performance liquid chromatography separations. Baseline separation of benzene, naphthalene, anthracene, and pyrene was achieved with the theoretical plate number for analyte naphthalene as 36 000 m^?1. Its separation function was further extended to cis/trans isomers of aromatic compounds where cis/trans stilbenes were chosen as a benchmark. Good separation of cis/trans‐stilbene with separation factor as 7 and theoretical plate number as 76 000 m^?1 for cis‐stilbene was obtained. The trans isomer, however, is retained more strongly, which contradicts the long‐ established retention rule of Ag ion chromatography. Such behavior of Ag nanoparticles embedded in a silica column can be attributed to the differences in the molecular geometric configuration of cis/trans stilbenes.     

Visco-elastic properties of reentrant nematic liquid crystalline mixtures

The visco-elastic properties for binary mixtures of 4-n -hexyloxy-4′-cyanobiphenyl (6OCB) and 4-n-octyloxy-4′-cyanobiphenyl (8OCB) are investigated in detail by a light scattering technique. The mixtures exhibit a reentrant nematic (RN) phase between the smectic A (SmA) and crystal phases in the range 22.0–29.5 wt % of 6OCB. The viscosity and the elastic constant increase with cooling in both the nematic and reentrant nematic phases. It is also found that the mixtures exhibit anomalously large values of viscosity and elastic constant near the phase transition, i.e. a pretransitional phenomenon can be observed. The activation energy for viscosity is smaller in the RN phase than in the ordinary nematic phase appearing at higher temperatures, while the normalized elastic constant (defined as the ratio of the elastic constant to the square of the dielectric anisotropy) is larger. Moreover, the visco-elastic behaviour depends on the specific time during which the sample has been kept in the SmA phase. These results confirm that the SmA phase has a strong influence on the formation of molecular aggregates, which plays an important role in the reentrant phenomenon of these systems.     

Synthesis of Star-Shaped Polymers via Coordination of Bipyridyl-Terminated Polyoxyethylene with Metal Ions

Abstract

This paper describes the synthesis of various star-shaped polymers by means of complexation of bipyridyl-terminated polyoxyethylene with Ru(II) ion. Three kinds of bipyridyl-terminated polyoxyethylenes of different molecular weights were prepared from the corresponding polyoxyethylene monomethyl ethers with narrow molecular weight distributions. Bipyridyl was found to be introduced quantitatively at the end of the polymers based on the results of UV spectra. The formation of a star-shaped polymer was carried out by the reaction of RuCl₃ with three equivalents of bipyridyl-terminated polyoxyethylene. The UV spectrum of the star-shaped polymer obtained supported the formation of a typical Ru(II) tris(bipyridyl) complex. From the results of GPC, the star-shaped polymer obtained had a higher molecular weight than the pre-polymer and showed a narrow molecular weight distribution. In the case of a Ni(II) or a Co(II) complex, however, the star-shaped polymer was found to be dissociated into three linear prepolymers under the conditions of GPC measurement.     

Saccharide Recognition by a Three-Arm-Shaped Host Having Preorganized Three-Dimensional Hydrogen-Bonding Sites

Generally, cage-shaped hosts for saccharides can bind strongly to guest molecules because of the three-dimensional preorganized hydrogen-bonding sites. However, the preparation of cage molecules is often difficult because of the low yield of the macrocyclization step. Here, we report a three-arm-shaped molecule possessing pyridine-acetylene-phenol units as a new kind of host having a preorganized three-dimensional hydrogen-bonding site. This three-arm-shaped host was readily prepared compared to a cage-shaped analogue. This host associated with lipophilic glycosides to form chiral complexes, and the association constants were sufficiently high as to be comparable to those of the cage-shaped analogue. Furthermore, this host extracted native monosaccharides into a lipophilic solvent.